Map Addict

As a matter of economy as well as convenience, that meridian should be selected which is now in most general use. This additional consideration of economy would limit our choice to the meridian of Greenwich, for it may fairly be stated upon the authority of the distinguished Delegate from Canada that more than 70 per cent of all the shipping of the world uses this meridian for purposes of navigation.

The French delegation were horrified, and filibustered the proposal off the table, with a speech by their prime delegate, M. Janssen, the Director of the Paris Observatory, that culminated in his demanding more time to consider the question but which, to reach that point, took well over an hour as he pondered the enormity of the matter in hand. He voiced their opposition to Greenwich in the most tremulously righteous terms:

This meridian, instead of being chosen with reference to the configuration of the continents, is borrowed from an observatory; that is to say, it is placed on the globe in a hap-hazard manner, and is very inconveniently situated for the function that it is to perform…Instead of profiting by the lessons of the past, national rivalries are introduced in a question that should rally the goodwill of all…Since the report considers us of so little weight in the scales, allow me, gentlemen, to recall briefly the past and the present of our hydrography, and for that purpose I can do no better than to quote from a work that has been communicated to me, and which emanates from one of our most learned hydrographers. ‘France,’ he says, ‘created more than two centuries ago the most ancient nautical ephemerides [tables showing coordinates of celestial bodies at particular times] in existence. She was the first to conceive and execute the great geodetic operations which had for their object the construction of civil and military maps and the measurement of arcs of the meridian in Europe, America and Africa. All these operations were and are based on the Paris meridian’. If another initial meridian had to be adopted, it would be necessary to change the graduation of our 2,600 hydrographic plates; it would be necessary to do the same thing for our nautical instructions, which exceed 600 in number.

Although happy to have a good sulk about how much more inconvenient a change of meridian would be for the French than anyone else, Janssen knew well that there was little mileage in further banging the drum for the Paris Meridian, whose cause was already lost. He seized instead on a more nebulous point that, he hoped, would sink the cause of the British, demanding of the conference that ‘the initial meridian should have a character of absolute neutrality…and in particular especially should cut no great continent—neither Europe nor America’. While Britain pretended to be above such squalid argument, their attack-dogs, the American delegation, weighed in with ready answers: ‘The adoption of the meridian of Greenwich has not been sought after by Great Britain,’ Commander Sampson boomed back. ‘It was not her proposition, but that she consented to it after it had been proposed by other portions of the civilised world.’ How very gracious of us: we can only imagine the holier-than-thou expressions adopted by the British delegation at this point. In his opening address, the American Admiral Rodgers had presaged this question of neutrality:

Should any of us now hesitate in the adoption of a particular meridian, or should any nation covet the honor of having the selected meridian within its own borders, it is to be remembered that when the prime meridian is once adopted by all it loses its specific name and nationality, and becomes simply the Prime Meridian.

Absolute horse-shit of course, but high-minded horse-shit of the finest grade. The Americans were really getting the hang of this diplomacy lark.

M. Janssen was the undoubted star of the event, able to turn in grandiloquent speeches, on any topic, that lasted an hour or two. Realising that the neutrality argument was all that lay in the way of the adoption of Greenwich, he worried at it like a starving poodle:

An immense majority of the navies of the world navigate with English charts; that is true, and it is a practical compliment to the great maritime activity of that nation. When this freely admitted supremacy shall be transformed into an official and compulsory supremacy, it will suffer the vicissitudes of all human power, and that institution [the meridian], which by its nature is of a purely scientific nature, and to which we would assure a long and certain future, will become the object of burning competition and jealousy among nations.

Anyone particular in mind, Monsieur?

Professor J. C. Adams, of the British delegation, waspishly replied that Janssen’s ‘eloquent address, in so far as I could follow that discourse, seemed to me to turn almost entirely upon sentimental considerations’, and reiterated the point of practicality, that the most ‘convenient’, i.e. widely used, meridian would make the most sense. He didn’t sully his purity by naming it; he didn’t need to.

In turn, Janssen rebuffed Adams in the politest way possible, while managing a few withering digs at his British counterparts (‘and we are still awaiting the honour of seeing the metrical system for common use in England’). He protested—rather too much—that the French objection was nothing whatsoever to do with ‘national pride’ and questioned the idea of the ‘convenience’ of the Greenwich Meridian. To whom exactly, he postulated, was it convenient? Ah, the Brits and the Yanks: the ‘advantage is to yourselves, and those you represent, of having nothing to change, either in your maps, customs or traditions—such a solution, I say, can have no future before it, and we refuse to take part in it’. He persevered in even darker tones: ‘You see, gentlemen, how dangerous it is to awaken national susceptibilities on a subject of a purely scientific nature.’ Ratcheting up his rhetorical powers, he concluded one particularly long speech with a flourish: ‘Whatever we may do, the common prime meridian will always be a crown to which there will be a hundred pretenders. Let us place the crown on the brow of science, and all will bow before it.’

Janssen’s sterling verbosity was only delaying the inevitable, so, realising that they were backed into a corner, the French hit their nuclear button, issuing veiled threats that they might walk out of the conference and then, when that went almost unnoticed, strident complaints about the standard of translation into their language at the conference. They demanded a recess in order to find a better French stenographer, a process that kept the conference from reconvening for a full further week. When all the delegates reassembled on Monday 13 October, everyone’s positions, after seven days of backstage back-stabbing, had coagulated into immutability.

The French kicked off proceedings by playing what was their only remaining decent card, the demand for the ‘absolute neutrality’ of any chosen meridian. It was put to the vote and heavily defeated by 21 to 3. As a faintly placatory gesture, Sandford Fleming, one of the British delegation, invoked the idea of placing the Prime Meridian 180° from Greenwich, thus, he said, giving it some political neutrality and positioning it largely in the uninhabited Pacific Ocean. The idea didn’t mollify the French at all, who sneered that even if the Prime Meridian was 180° from Greenwich, it was still the Greenwich Meridian in all but name, only in reverse.

This proposal from the British delegation was typical of our fauxhumble demeanour at this stage in the proceedings: it’s easy to be magnanimous when you’re clearly winning, especially in a contest that you’re feigning absolute disinterest in. The British vat of oil to pour on troubled waters was soon generously employed again, as the French and Spanish reminded delegates that their governments fully expected Britain and the USA to join the metric system, if not in a quid pro quo for the adoption of Greenwich, then certainly in the same spirit of global good manners and scientific unity. One of the British delegation, General Strachey, smoothly replied:

I am authorised to state that Great Britain, after considering the opinions which were expressed at Rome, has desired that it may be allowed to join the Convention du mètre…[and] that there is a strong feeling on the part of the scientific men of England that, sooner or later, she will be likely to join in the use of that system, which, no doubt, is an extremely good one.

In other words, we’ll get home and do precisely nothing about it for a century, but thank you so much for your concern. Stuff you with a smile, Monsieur.

The definitive vote on adopting Greenwich loomed, and the French made one last desperate bid to prevent it. The loquacious M. Janssen deferred to his colleague M. Lefaivre to make their final plea. ‘The meridian of Greenwich is not a scientific one,’ piped Lefaivre, ‘and its adoption implies no progress for astronomy, geodesy or navigation.’ It was only ‘convenient’, not scientific, a fact that

our colleague from Great Britain just now reminded us of by enumerating with complacency the tonnage of British and American shipping…Science appears here only as the humble vassal of the powers of the day to consecrate and crown their success. But, gentlemen, nothing is so transitory and fugitive as power and riches. All the great empires of the world, all financial, industrial and commercial prosperities of the world have given us a proof of it, each in turn.

This was the sound of grand nobility in defeat, for the vote was then taken and Greenwich confirmed as the world’s Prime Meridian by 22 votes to 1, with two abstentions. Only San Domingo (the island of Hispaniola) voted against, with Brazil and France abstaining. They didn’t want to look like sore losers. Or rather, they were saving that for later.

After further lengthy arguments about how to calibrate degrees from Greenwich, and how to calculate time zones, the French asked for another deferment of the conference. They returned six days later with a small bombshell of a proposition: that the metric system—which, they reminded delegates, everyone had spoken so voluminously in favour of—should be extended from the measurement of length, volume and weight and into the realms of degrees, angles and time. Greenwich might be getting the line through it, but at least the grid of longitude and the calibration of the day that spun off it might be expressed in a French way, or at least in a way that was guaranteed to piss off the Anglo-American alliance. The British and the Americans cried foul, that such a decision was beyond the remit of the conference.

Style over substance: the Paris meridian

For the first time in weeks, the French smelled English-speaking blood and pressed home their slender advantage, demanding a vote on whether or not a vote could be taken on the topic. It was close. Thirteen countries agreed that the issue of metricising time and angles could be considered; nine, Britain and the US included, voted against. Two abstained. So, as eager not to appear bad losers as had the French been on the Greenwich vote, the Americans and British then ostentatiously supported the metric system in the subsequent vote. In fact, no one voted against it—not that that made the faintest bit of difference in actually making it happen.

Flushed with their pyrrhic victory, the French demanded a further adjournment to the conference, which briefly reconvened two days later before its final adjournment, for nine days, in order that the conference protocols could be drawn up, in English and, of course, in French. On the first of November, a month to the day since the delegates had first gathered, the conference closed in a mutual orgy of back-slapping and vainglorious speeches about how the international community was united as never before and that they had made history. Thankfully, the sagging balloon of hot air was peremptorily pricked by the very last contribution noted in the conference minutes: the ever vocal M. Janssen of the French delegation complaining about the standard of French used in their translations.

As expected, the French reaction to the conference’s decision was to ignore it for as long as they possibly could. The Paris Meridian was still marked as 0° on French maps until 1911, and even beyond that, they kept refusing to refer to the notion of Greenwich Mean Time, preferring instead to name the concept the altogether snappier ‘Paris Mean Time diminished by 9 minutes 21 seconds’. It’s a shame it didn’t catch on: PMT has such an appropriate ring to it for matters of timekeeping. Even though the Paris Meridian has long been shunted into the sidings, the French still keep polishing it and showing it off to the world like a priceless relic. One of their main millennium projects was to plant lines of trees the entire length of France along their old meridian line. It might no longer be functioning, but hey, you could see it from space, or at least if you look closely enough on Google Earth in a few decades’ time. To a chippy Brit (and, when it comes to any dealings with the French, that’s most of us), the project smacked of dismissive looking down the Gallic nose at the lack of presentational flair that attends our meridian line.

The world’s timekeeping and cartographic staff it may be, but as the Prime Meridian enters Britain in the retirement town of Peacehaven on the Sussex coast, it’s marked only by a dowdy obelisk and the Meridian Centre, a deathly 1970s shopping mall with the unmistakable aroma of incontinence. Two hundred and three miles due north, it leaves English soil in similarly dreary fashion, on a beach just south of the Sand-le-Mere caravan park, near Tunstall on the Holderness coast of Yorkshire’s East Riding. Britain’s bleakest coast is also

Substance over style: where the Prime Meridian enters England at Tunstall, East Yorkshire

the fastest-receding in Europe, where houses and roads tumble regularly over the edge, leaving their forlorn traces to be washed over by a freezing sea the colour of a river in high flood. In the circumstances, the great local millennium project—placing a huge carved boulder on the cliff top to mark the point at which the global meridian arrives in its home country from the North Pole—was something of a triumph of optimism over experience. Instead of lasting the full thousand years, it managed just three, disappearing over the muddy cliff in a storm in January 2003. In between these two inauspicious gateposts, as well as the whistles and bells of Greenwich itself, the meridian is marked by a number of plaques, columns, archways and, in Cambridgeshire, a line of daffodils planted by Boy Scouts. It’s either disarmingly modest or just a bit crap. Either way, it’s British through and through.

If—and, frankly, it’s a bloody big if—we accept British pre-eminence in modern mapping owing to the adoption of the Greenwich Meridian as the gold standard for measuring lines on a map, then one event gave birth to this certainty. That was the creation of an earlier imaginary line on the landscape, the first precisely calibrated base line across a stretch of English countryside, from which all initial triangulations were taken to produce what soon became the Ordnance Survey. It took place in the summer of 1784, and for reasons that are also gloriously British: once again, a fierce spirit of one-upmanship against the French and a supremely thin-skinned paranoia that they were insulting us.

We had a lot of making up to do; by the late eighteenth century, French map-making was leagues ahead of that of its clod-hopping British cousin. Nearly a century earlier, their experiments in establishing accurate lines of longitude and latitude had proved that the world was an oblate spheroid, rather than a perfect sphere, which had tremendous impact on the precise measurement of relative distances, radically altering the shape and size of France itself as presented on a map. Coupled with advances in triangulation and surveying, the Académie Royale produced, in 1789, by far the finest and most ambitious cartography that had ever been made of one country: a complete set of 180 maps, covering all of France, at a scale of 1:86 400, just under one and a half miles to the inch. Even the detail on the maps was starkly different: while we were still delineating our upland areas with crude shading or lumpy molehills scattered over the landscape, the French were developing sophisticated systems of hachures—groups of parallel lines to indicate height—before pioneering the use of contour lines on some maps from the 1750s.

The year 1789 is better remembered in France for rather bloodier reasons than the publication of the national map, the Carte de Cassini as it became known, after César-François Cassini de Thury, the Director of the Paris Observatory and its principal progenitor, who had died of smallpox in 1784, leaving his son to continue the work. The new revolutionary government looked with grave suspicion on anything royale, the Académie included, although they were more than delighted with the maps and promptly took over all responsibility for their production and publication. The Académie Royale was closed down (to resurface a few years later as the more egalitarian Académie des Sciences), Cassini junior was imprisoned, while Académie director Antoine Lavoisier was carted off to the guillotine. It was at just this moment in history that the British were starting to get their act together, and, aided by the chaos in France, were soon able to outstrip their neighbours. Though, as ever, it took some pompous prodding by the French to sharpen us up.

That came six years before the Revolution, in the shape of a missive from Cassini de Thury to King George III, in which he loftily pointed out that the world’s two principal meridians, those of Paris and London, were out of kilter in both longitude and latitude. His inference was that, thanks to the superior surveying and triangulation of the French, the mistake was almost certainly on our side of the Channel, and would His Majesty care do something about it? He further rubbed salt into the wounds by pointing out that he himself had checked the trigonometry on the French side all the way up to the Channel coast, and, using a telescope, had established many landmarks on the English side that could be useful if we could be bothered to do a proper survey. The King’s principal Secretary of State, Charles James Fox, passed on the letter to Sir Joseph Banks, President of the Royal Society in London. Many of its members were outraged by the slurs it contained, the Astronomer Royal, the Reverend Doctor Nevil Maskelyne, firing off a hasty rebuttal of the French claims. But there was one Fellow of the Royal Society who received the news with equanimity, bordering on glee, for he knew that this was the chance for which he had been waiting for decades.

We know frustratingly little about Major-General William Roy (1726-90), a map addict of impeccable credentials and the father of the Ordnance Survey. No portrait survives of him, few biographical details have come our way, but, from his plans, letters and publications, we can see a man utterly driven by maps and an insatiable urge to make them ever better. He started in his native Scotland, working with the surveying crews that had been drafted in as a response to the Jacobite uprisings in the Highlands of the 1740s. The official response was the same as always: go deep into enemy turf, build roads and military outposts, move the population to where they could better be tracked, and, most importantly of all, comprehensively map it. For years, this was Roy’s day job, though, as a sideline, he also worked obsessively to map the Roman remains of Scotland, for they had employed much the same techniques in suppressing the clans fifteen centuries earlier. There’s not much doubting what his specialist subject would have been on Georgian Mastermind.

The first survey of Scotland, between 1747 and 1752, was of the troublesome Highlands, when Roy was teamed up with the young Paul Sandby (1731-1809). Sandby, who later became one of the age’s most celebrated landscape painters and a founder member of the Royal Academy, provided the artistic talent for the beautiful maps that they produced, complementing Roy, the technical wizard who worried perpetually about getting the topographical detail correct. Once the Highlands had been comprehensively mapped, it was decided to survey and plot southern Scotland, but Sandby had returned to England by then and the resultant maps were nowhere near as spectacular as the earlier ones of the far north. Roy was a perfectionist, and the lack of precise measuring equipment frustrated him enormously; late in life, he wrote about these early map-making efforts in Scotland, describing them as ‘rather a magnificent military sketch, than a very accurate map of a country’.

From Scotland, Roy enlisted in the army and served with distinction in the Seven Years’ War with France. Once again, his map-making skills, and perfectionism, were usefully employed in his work as a special adviser on troop deployment and strategy. Roy’s reports on such matters included beautifully drawn maps that he always insisted on doing himself, the army draughtsmen and his subordinate officers just not being up to his exacting standards. This lack of trust in anyone else became a growing theme as his career moved towards its apogee.

On his return, he settled in London, and continued rising through the ranks of the army, while spending more and more time on his cartographic pursuits. Central to his ambition was finding the right equipment, or rather, having the right equipment created for his needs. Much of his time was spent experimenting with measuring instruments in order to see how they could be employed to produce the greatest possible accuracy. They were never quite good enough. Nonetheless, his military experiences abroad, and his knowledge of how far advanced the Dutch and French were in such matters, had convinced him that the time was ripe for a comprehensive national survey, and he first approached the authorities about the matter in 1763. With a canny knack for telling the government what he most thought they would respond to, he emphasised Britain’s vulnerability to invasion, particularly along the south coast, and the importance of conducting such a survey ‘during times of peace and tranquillity’, rather than waiting to do it under the chaotic cloud of war. They turned him down on grounds of expense. He re-presented his plans three years later, only to have them refused once again.

Impatient but undeterred, William Roy used every moment of his spare time to conduct his own informal triangulation experiments around London, establishing the position and distance of landmarks in the capital in relation to the Royal Observatory at Greenwich. Triangulation remained the bedrock of map-making until it was supplanted, less than thirty years ago, by satellite Global Positioning Systems (GPS) technology. The principle of triangulation is that if you know the length of one line of a triangle, and two of its angles to the other lines, the entire triangle can accurately be plotted for both distance and elevation. It’s an extremely time-consuming business, depending as it does on caddying heavy equipment up to the highest vantage points: the first triangulation of Britain and Ireland, started by William Roy in 1783, took nearly seventy years to complete.

Roy regularly presented his London triangulation findings to the Royal Society, so that when the inflammatory missive came from Paris in 1783, he seemed the obvious man to restore Britain’s dented honour by conducting the experiment. He was extremely well prepared, for he had used every one of his travels, both at home and abroad, to map the landscape and establish the most suitable places for triangulation. The flat expanse of Hounslow Heath, to the west of London, had long been selected as his preferred choice for the perfect base line. And although the project was nominally to establish only the precise relation of the London and Paris observatories, Roy knew well that it could, and should, be the harbinger of something far greater; that it could ‘extend different serieses [sic] of Triangles…in all directions to the remotest part of the Island’.

William Roy is an undoubted hero to any British map addict, but he is also something of a siren warning to us all. The brilliant young adventurer turned inexorably into a grumpy old man, for whom no one, and nothing, was ever quite good enough. Sounds familiar? I rather fear so. So fixated did he become by his great triangulation project that he picked fights with anyone who failed to come up to his exacting standards, most spectacularly in the case of instrument-maker Jesse Ramsden (1735-1800). Ramsden was just as much of a perfectionist as Roy, and with just as great a cause: his scientific and astronomical instruments attracted customers from across the world to his Piccadilly workshop. Roy’s greatest frustration throughout his map-making career was the fact that the measuring instruments available couldn’t cope with the precision that he demanded. For the great triangulation project of south-east England, Roy commissioned Ramsden to design and build the most exact theodolite ever seen.

Unfortunately, Ramsden failed to employ enough workmen on the project and thus to produce the goods soon enough for Roy, and the cartographer began to cast increasingly bellicose aspersions on the instrument-maker’s professional ability. The massive theodolite—it weighed over fourteen stone and had to be hauled around on a specially designed truck—was the finest ever created, but, to Roy’s continuing chagrin, it was still prone to some tiny errors and, most annoyingly, took a whole three years to build. In fairness to Roy, he was sixty years old and in failing health, so must have felt the continued delays with increasing impatience, urgently wanting to finish the project while he still could. That doesn’t excuse his behaviour, however, as he repeatedly complained about Ramsden to the Royal Society in letters and papers that became ever more dyspeptic. Ramsden, also a Fellow of the Society, responded in kind, so that members found themselves piggies-in-the-middle as complaints and counter-complaints between the two men resounded throughout the Society’s hallowed halls. Roy charged Ramsden with being ‘remiss and dilatory’ and ‘very negligent’; Ramsden whined back that ‘nothing could equal my surprise on hearing the charges brought against me by Major-General Roy…I was the more affected by it as coming from a Gentleman with whom I considered myself in Friendship’. This spat reached its climax in May 1790, when Ramsden demanded that the Royal Society expunge some of Roy’s more colourful slaggings of him from their records. Sadly, William Roy died a few weeks later, the matter still unresolved. It was an acrimonious—and, to us, salutary—end to a brilliant career.

Although William Roy died before the official foundation of the Ordnance Survey in 1791, he was its undoubted progenitor. The event that gave formal birth to the organisation was the re-measuring of the Hounslow Heath base line that Roy himself had first established some seven years earlier. In April 1784, following the French submission to George III, Roy had swiftly secured government backing for the survey and wasted no time in getting on with it. He had at his command twelve Army NCOs and an entire division of the 12th Foot Brigade from nearby Windsor; these he set to levelling and clearing the five-mile-plus route of his line. Having a burly crew of soldiers around was also good insurance; Hounslow Heath in the eighteenth century was the most dangerous location in Britain, and certainly not a place for gentlemen to linger. London and Bath were the two wealthiest cities in Georgian England, and the busy road connecting them ran (as it does still) along the heath’s northern edge. The lowlying ground, with its unexpected fogs, suppurating ditches and numerous copses, was the ideal hiding place for highwaymen and cutpurses, who had rich pickings among the well-to-do on their way to Windsor or the West Country. Contemporary maps show a string of gibbets along the Bath Road across the heath. Many of these would have contained rotting corpses swinging in the breeze, for the policy of the authorities was to return the bodies of those hanged at Tyburn to the place of their misdemeanours, to be displayed to all as a shocking deterrent.

Jesse Ramsden—still, at this point, in Roy’s good books—had made a steel chain exactly one hundred feet in length, together with wooden rods of twenty feet apiece: both were used alternately to calibrate the distance as the party progressed slowly from King’s Arbour Field and across the heath, with the distant witch’s hat spire of Banstead church as their guidance point on the horizon. Work progressed through a monumentally wet summer, conditions that didn’t suit the wooden rods, which were found to expand and contract way too much for accurate measurement. The project ground to a brief halt. Glass rods were commissioned and produced, which required the utmost delicacy as they were hauled across the heath, particularly when it came to crossing the busy Staines Road.

Delays occurred too because the surveying team became something of an unlikely attraction, especially after King George III dropped by on 19 July to see how the work was going: unfortunately, so torrential was the rain that Roy was unable to demonstrate much of their work. The King returned on 21 August and spent two hours examining the team’s work and discussing it with them. This, according to Roy, ‘met with his gracious approbation’. In his wake, all manner of society notables trotted by to see what was going on, and it was left to Sir Joseph Banks, the President of the Royal Society, to erect mobile refreshment and hospitality tents in order to cope with the crowds and to keep them at a discreet distance from the work of the surveyors. The team finally reached their destination, the workhouse at Hampton, on the penultimate day of August. By now, the steel chain had been abandoned and the entire measurement had been made using the glass rods. The base line, announced William Roy, was 27,404.72 feet: just over 5.19 miles long. ‘There never has been,’ he declaimed, ‘so great a proportion of the surface of the Earth measured with so much care and accuracy.’

Three years later, when Ramsden’s theodolite was finally ready, the survey continued, using triangulation to work its way from Hampton down to Dover and the English Channel. The supposed aim of establishing the precise relation of the London and Paris observatories was never quite attained, but the process had, in Roy’s eyes, been hugely successful in his main ambition of showing how poor and imprecise current British maps were and how a national survey was both urgently desirable and eminently practicable. In his final report to the Royal Society and the King in 1789, Roy egged them all on:

The trigonometrical operation, so successfully begun, should certainly be continued, and gradually extended over the whole Island. Compared with the greateness of the object, the annual expence to the publick would be a mere trifle not worthy of being mentioned. The honour of the Nation is concerned in having at least as good a map of This as there is of any Other country.

Such as France, Your Majesty, he might have added. It took less than a year for the authorities to agree and to find the money, but, by then, Roy was dead.

The fogs, footpads and gibbets may be long gone from Hounslow Heath, but the land still has a melancholy tang to it, if only thanks to the fact that so much of it has been eaten alive by Heathrow Airport, located there for precisely the same reasons (vast expanse, flat as a pancake, near London) as Roy’s base line. The airport has swallowed whole villages along the northern part of the line, its route south-east has been filled in with shops, factories, houses, roads and all the normal suburban detritus of the outskirts of London. The line, dotted across field and factory, and marked portentously as General Roy’s Base, used to appear on OS maps up until the early twentieth century, though not since. Strangely, the northern end of it at Heathrow is labelled, on the current OS 1:25 000 Explorer map, with the supremely wordy ‘Cannon: West End of General Roy’s Base (site of)’; although the cannon is firmly there in precisely the spot indicated, there is nothing ‘site of’ about it. The other end, at Hampton—which is far easier, and more pleasurable, to find—doesn’t even warrant that, and goes completely unmarked.

Trying to trace the line today, I was reminded of the late Linda Smith’s immortal observation that Greater London was something of a misnomer, for ‘the further you get away from the middle of it, London doesn’t really get greater—it’s more Lesser London’. She came from Erith (‘not so much the city that never sleeps, more the town that lies awake all night staring at the ceiling’), which sits crusted on the rim of the capital in much the same way as Feltham, Bedfont and Hanworth, the sprawls that now cover William Roy’s historic line. There are other invisible lines to contend with here: these undistinguished, indistinguishable towns are firmly on the other side of the tracks from leafy Hampton (as in Court), where Roy’s measurement ended. This lies in that weird little south-western corner of Greater London, the Twickenham-Richmond triangle: smug and tweaked, embarrassed Tory so voting LibDem, death by bungalow and leylandii.

After Major-General Roy conducted his experiments, wooden posts were interred in the ground at either end of the recorded base line as a memorial. In 1791, eleven months after Roy’s death, the party led by the Duke of Richmond, charged with re-measuring the line for the Board of Ordnance, found that the posts were rotting and so they were replaced by upended cannons. There, wondrously, they still remain. Both cannons have seen untold change unfold around them over two centuries. The southern one, at Hampton, witnessed the demolition of the borough workhouse nearby; it thence lived in an area of open ground known as Cannon Field until Twickenham Borough Council built housing estates on it in the late 1940s. At least they left the cannon intact and had the good grace to name the two nearest culde-sacs Roy Grove (where the cannon can be found sat in a grassy gap between two post-war semis) and Cannon Close (which, indeed, it is). This is Hampton as the acme of suburbia, so much so that the street opposite is Acacia Road.

Handily, there’s a bus—the 285 Kingston-on-Thames to Heathrow—that almost precisely connects the two cannons, taking a route that’s only a little over a mile longer than William Roy’s 5.19-mile straight line. The good general wouldn’t recognise it these days. The bus coughs its way up the Uxbridge Road and into Feltham, doing a quick detour into the Sainsbury’s car park, and passing forlorn-looking light industrial estates, the Clipper Cutz hair salon, the Chirpy Chaps barbers, Cindy’s Nail Bar, Fryday’s chippy, a Subway or two, the A3 roundabout and parades of Metroland semis displaying either a St George’s flag or a ‘No To Heathrow Expansion’ sticker, sometimes both (albeit quite hard to see through the triple glazing).

I broke my journey at Feltham, in order to take a look at another oblique memorial to William Roy, an eponymous modern pub off the High Street. This, it claims, is named after him because of its position more or less halfway along his historic line, although it’s stretching things slightly, as the General Roy pub is nearly a mile to the south of the route. There’s nothing there to indicate its homage to Roy, save for one old map of the district on the wall, showing the Feltham area as a bucolic cluster of villages, before they were entirely obliterated by the spreading gut of the capital and its main airport. The pub is pitched at workers from the nearby industrial park, home to something glassy and chromey called the Feltham Corporate Centre—a name to strike even greater terror into the loins than the town’s rather better-known Young Offenders’ Institution.