The Forgotten Guide to Happiness: The unmissable debut, perfect for anyone who loved THE KEEPER OF LOST THINGS

‘Yeah? Mine too.’

‘How old were you?’

‘Eighteen. You?’

‘Eight. It killed my mother.’

Mine, too, I almost said but then I looked up and his face was expressionless, as if he didn’t want his thoughts to show, so I held back my comment in case he meant it literally.

Of course, when I asked him what he thought of the book, what I actually wanted to know was whether he’d enjoyed it. Writers are strangely needy that way. Last year I went to the Radio Four book club and sat next to a woman named Minna Howard, who was also a writer (it was research, in case we were ever asked to do it ourselves), and the highly acclaimed guest author David Mitchell responded to her praise with such warmth and delight that I was convinced he was her ex-lover. Turned out she’d never seen him before in her life. He was just deeply grateful for her kind words.

We crossed at the lights and stepped into bright sunlight at Gloucester Gate. The sky was a pale, frigid blue. Attached to the railings was a plaque showing St Pancras being attacked by pumas. We crossed at the stone grotto drinking fountains where Matilda the bronze milkmaid posed with her bucket and he asked: ‘So, what happened to Marco Ferrari?’

I blushed. Well this was uncomfortable. When I’d written Love Crazy I’d assumed Mark and I would be together forever so I’d never imagined this situation arising – going out with a guy who knew all about my past.

I’ve always been obsessed with telling the truth and, although I see it as a positive character trait, other people don’t necessarily see it as a good thing. But I’ve stuck with it because it’s become my way of rebelling. No one can argue with the truth.

The way I looked at it, this meant that I was also going to have to explain that Mark had dumped me and it was way too soon to disillusion him – I always prefer people to get disillusioned with me in their own good time.

However, the habit of a lifetime is hard to break.

‘We broke up,’ I said, and glanced up at him, blinking – in the sunlight his lime-green jacket was hard on the eyes.

‘I knew it!’ Jack said. ‘So, what happened? Did you get bored with all that adventure and the excitement?’

I liked the way he assumed I’d been the one to end it. ‘We’d always kept our independence; I guess it was an extreme version of that.’

He pressed the button on the crossing. ‘Independence to the point of separation?’ He gave me a look that was both incredulous and empathetic at the same time. ‘And now you’re looking for a new hero to write about.’

I wanted to say something witty and trivial in reply. We crossed the road and while I was working on it, Jack said, ‘So, with the pedalo you really need two to pedal, that’s why I thought we could get a rowing boat and I could row you by myself.’

‘Have you rowed before?’

‘No, but I watch the boat race every year and I think it’s all about the rhythm. Brisk and steady.’

I laughed. There was an endearing quality about him; something normal and nice, and trust me, they weren’t attributes that I ever thought I’d rate in a guy. We walked in step alongside the Zoological Society of London’s railings, keeping a respectable distance away from each other.

Ahead of us was the park. In the golden glow of the autumn sunshine, the grass was bright green, and the trees striped it with muted shadows. A glossy brown boxer dog bounded across our path chasing pigeons and two children raced their brightly coloured scooters towards us with speed and aplomb. Joggers overtook mothers pushing buggies and I thought about Jack’s comment that love was time-consuming. I was just going to ask him about it when his phone started to ring right at that moment.

He took it out of his jacket, stared at the number and frowned. For a moment I thought he wasn’t going to answer it. He let it ring a couple more times and then he sighed.

‘Sorry, Lana, I’d better take this.’

‘Go ahead.’

I did that polite thing of staring at the horse chestnut trees in the distance and pretending not to listen as he said, ‘Hello? Nancy. Slow down – what do you mean, a lot of men? John the police officer?’ He flicked a glance at me. ‘Okay, okay, put him on. Hello? Yes,’ he said irritably, ‘I can hear that she’s fine. No, I’m not worried.’

He turned his back to me as he looked across the park. ‘A sex offender? What’s he done? What do you mean you can’t tell me? Okay. Put Nancy back on. Hi, Nancy, it’s Jack again. Listen, I’m out with a friend at the moment. I’ll call you later.’ His face was set as he turned back to me and tucked his phone away.

Obviously I was intrigued by what I’d heard. I hadn’t been a journalist for five years without knowing a good story when I heard one.

‘Problem?’ I asked lightly.

‘My stepmother’s had a drink with a sex offender. That’s all they would tell me.’

‘How did she know he was a sex offender? And how did the police get involved?’

‘Don’t ask me.’ He shrugged. ‘This always happens,’ he said grimly. ‘Every time. It’s as if – anyway, forget it, let’s crack on. Do you mind if we miss out the coffee and go straight to the boating lake?’

He strode off up the Broad Walk without waiting for an answer and I hurried to catch up with him as he cut across the grass.

I grabbed his arm. ‘Look, Jack, we don’t have to do the boating thing. We can go another day, I don’t mind.’

‘No,’ he said stubbornly, ‘it’s fine. I’ve planned it.’ But he stopped walking, his eyes narrowed with indecision. He rubbed his hands over his face and his grey eyes met mine and held. ‘I’m sorry. You’re right. I should go.’

‘Yes.’ I was more disappointed than I’d expected. He was easy to be with and he made me smile, but I could see the relief in his face and I knew that for once I’d said the right thing. ‘I hope you get things sorted out.’

Behind the railings, through gaps in the foliage, I could see the penguins standing at the edge of their blue pool, bracing themselves to dive, wings held at the ready before taking the plunge. ‘Well, thanks. It’s been—’

‘You could come with me,’ he said.

‘Really?’ Our day out wasn’t over! ‘Okay.’ I didn’t need asking twice.

We turned around and headed the other way, towards the road. The crossing beeped and the cars stood at bay and the green man showed, and we walked over the canal together even though the fake date was over and we weren’t going boating any more.

We caught the C11 bus from Adelaide Road and stood in the wheelchair area, crushed together. He was taller than Mark and I was eye-level with his throat. It was a nice throat; smooth and strong.

‘Your stepmother – did she break up your parents’ marriage?’

‘Yes. She was pretty ruthless about it. And my father was weak.’

‘How did she get to be your responsibility?’

He gave a brief laugh. ‘After my mother died I went to live with her and my dad. Then he died, so now it’s just Nancy and me. She was in her late fifties when she and my dad met so she doesn’t have children of her own.’

I thought about the way he’d said that heartbreak had killed his mother. But despite all that, he was still looking out for Nancy. I tried to imagine being that dutiful towards Jo-Ann and failed miserably.

We got off at South End Green and walked up South Hill Park. The house was four-storey, red-bricked Victorian; it backed onto the other side of Parliament Hill Fields. I could probably see it from my window. A police car was parked up against the kerb. Jack rang the doorbell and a community police support officer answered the door; she had short dark hair and an attitude that indicated we shouldn’t mess with her.

‘We’ve taken a statement,’ she told Jack in the hallway.

To the side of the chandelier above her head loomed a huge oil painting of an old lady with a skinny black and white dog. They were looking into an empty cupboard with some dismay.

It seemed a strange choice of picture. I had built up an image of Nancy as an older woman clinging onto her youth with yoga, Pilates and Botox; I’d imagined she’d go for something more modern, an abstract.

‘She seems fine, but she’s vulnerable.’

‘She’s eighty,’ Jack said.