I want to add what I really feel, which is: ‘I wish Daddy had never sold that house,’ but it probably wouldn’t go down well. Nor will I admit that my memories are a tad hazy. The point is, I want to go back.

Dan’s silent. His face is motionless. It’s as if he can’t hear me. Or maybe he can hear me, but something else in his head is louder and more insistent.

My energy levels are sinking. There’s only so many times you can try. Sometimes I feel his issue with my father is like a huge boulder, and I’m going to have to push it and drag it and heave it along beside us, our whole marriage.

‘Fine,’ I say at last. ‘Where shall we go next year?’

‘I don’t know,’ says Dan, and I can tell he feels defensive. ‘Somewhere in Britain, maybe.’

‘Like an organic garden?’ I say pointedly, but I’m not sure Dan gets my little dig. I’m about to add, ‘I hope you’ve got your snake-sitter lined up,’ when Tessa comes running in, her mouth an ‘O’ of horror.

‘Mummy!’ she cries. ‘Mummeeee! We’ve lost our stomp rocket!’

As Professor Russell answers the front door, his eyes seem to have a glint of humour in them, and I suddenly wonder: did he hear me yelling at Dan just now? Oh God, of course he did. They’re not deaf at all, are they? He and Owen probably sit and listen to Dan and me as though we’re The Archers.

‘Hello,’ I begin politely. ‘I’m so sorry to disturb you, but I think my daughter’s rocket has landed on your greenhouse. I do apologize.’

‘My stomp rocket,’ clarifies Tessa, who was determined to accompany me on this little visit and is clutching my hand.

‘Ah. Oh dear.’ Professor Russell’s eyes dim, and I can tell he’s got visions of Dan climbing up and cracking his glass.

‘I’ve brought this,’ I say hastily, and I gesture at the telescopic broom in my hand. ‘I’ll be really gentle, I promise. And if I can’t reach it, then we’ll get the window cleaner to do it.’

‘Very well.’ The professor’s face relaxes into a smile. ‘Let’s “give it a go”, as they say.’

As he leads us through the house, I look curiously about. Wow. Lots of books. Lots of books. We pass through a bare little kitchen and a tiny conservatory furnished with two Ercol chairs and a radio. And there, dominating the garden, is the greenhouse. It’s a modernist structure of metal and glass, and if you put a kitchen in it, it could totally go in an interiors magazine.

I can already see our stomp rocket, looking incongruous and childlike on the glass roof, but I’m more interested in what’s inside. It’s not like other people’s greenhouses. There aren’t any tomatoes or flowers or wrought-iron furniture. It’s more lab-like. I can see functional tables and rows of pots, all containing what looks like the same kind of fern at different stages of growth, and a computer. No, two computers.

‘This is amazing,’ I say as we approach. ‘Are these all the same kind of plant?’

‘They are all varieties of fern,’ says Professor Russell with that glimmering smile he has, as though sharing a private joke with someone. (His plants, probably.) ‘Ferns are my particular interest.’

‘Look, Tessa.’ I point through the glass panes. ‘Professor Russell has written books about these ferns. He knows everything about them.’

‘“Knows everything about them”?’ Professor Russell echoes. ‘Oh my goodness, no. Oh no, no, no. I’m only just beginning to fathom their mysteries.’

‘You’ve been studying plants at school, haven’t you, darling?’ I say to Tessa. ‘You grew cress, didn’t you?’ I’m suddenly wondering if we could get Professor Russell to go into the girls’ primary school and give a talk. I would get major brownie points.

‘Plants need water,’ recites Tessa, on cue. ‘Plants grow towards the light.’

‘Quite right.’ Professor Russell beams benevolently at her, and I feel a swell of pride. Look at my five-year-old, discussing botany with an Oxford professor!

‘Do people grow towards the light?’ Tessa says, in that joking way she has.

I’m about to say, ‘Of course not, darling!’ and share an amused glance with Professor Russell. But he says mildly, ‘Yes, my dear. I believe we do.’

Oh, OK. That tells me.

‘We have, of course, many different kinds of light,’ Professor Russell continues, almost dreamily. ‘Sometimes our light might be a faith, or an ideology, or even a person, and we grow towards that.’

‘We grow towards a person?’ Tessa finds this hilarious. ‘Towards a person?’

‘Of course.’ His eyes focus on something beyond my shoulder and I turn to see Owen coming down the path.

I haven’t seen Owen close up for a while, and there’s something about him that makes me catch my breath. He looks translucent, somehow. Frailer than I remember. His white hair is sparse and his bony hands are painfully thin.

‘Good morning,’ he says to me in a charming though hoarse voice. ‘I came to see if our visitors would like coffee.’

‘Oh, no thanks,’ I say quickly. ‘We’re just here to get our toy. Sorry for all the noise,’ I add. ‘I know we make a bit of a racket.’

I can see Professor Russell’s eyes meeting Owen’s briefly, and I’m suddenly sure without a doubt that they’ve heard me and Dan fighting. Great. But almost at once, Owen smiles kindly at me.

‘Not at all. Nothing to apologize for. We enjoy hearing the children play.’ He eyes the broom in my hand. ‘Ah. Now that’s ingenious.’

‘Well,’ I say doubtfully. ‘We’ll see.’

‘Don’t wait out here.’ Professor Russell pats Owen’s hand. ‘You can watch our efforts from the conservatory.’

As Owen retreats towards the house, I extend the broom handle and reach up, and after just a few jabs, the stomp rocket falls down into my arms.

‘Well done!’ applauds Professor Russell. Then he turns to Tessa. ‘And now, my dear, may I give you a little plant as a souvenir? You’ll have to water it, mind, and look after it.’

‘Oh, that would be lovely!’ I exclaim. ‘Thank you!’

I’m thinking: I’ll put Dan in charge of the plant. That is, if he really is into gardening and not just into dimpled ex-girlfriends.

Professor Russell potters into the greenhouse and emerges with a small green frondy thing in a pot.

‘Give it some light, but not too much,’ he says, his eyes twinkling at her. ‘And watch how it grows.’

Tessa takes the pot, then looks up at him expectantly. ‘But we need one for Anna,’ she says.

‘Tessa!’ I exclaim, appalled. ‘You don’t say that! You say, “Thank you for the lovely plant.” Anna’s her twin,’ I explain apologetically to Professor Russell. ‘They look out for each other. You can share it with Anna,’ I add to Tessa.

‘Not at all!’ says Professor Russell at once. ‘Tessa’s quite right. How could we forget Anna?’

He darts back into the greenhouse and produces a second little plant.

I wince. ‘I’m so sorry. Tessa, you mustn’t ask for things.’

‘Nonsense!’ Professor Russell winks at Tessa. ‘If we don’t stick up for the ones we love, then what are we good for?’

As Tessa sinks to her haunches and begins examining the plants more closely, Professor Russell’s gaze drifts again over my shoulder. I turn and see that he’s watching Owen, who is settling himself in one of the Ercol chairs in the conservatory, a blanket over his knees. I can see Professor Russell mouthing, ‘Are you all right?’ and Owen nodding.

‘How long have you two been …’ I ask softly, not quite sure how to put it. I’m fairly sure they’re not just friends, but you can never be sure.

‘We knew each other as schoolboys,’ says Professor Russell mildly.

‘Oh, right,’ I say, taken aback. ‘Wow. That’s a long time. So …’

‘At that time, Owen didn’t realize his … true nature, shall we say.’ Professor Russell blinks at me. ‘He married … I devoted myself to research … We found each other again eight years ago. In answer to what I believe you are asking, I have loved him for fifty-nine years. Much of it from afar, of course.’ He gives that glimmering smile again.

I’m speechless. Fifty-nine years? As I survey his wrinkled face, I feel like Professor Russell towers above me in every way. He has a towering intellect. A towering love. I have an urge to stay here and ask him lots of questions and soak up some of his wisdom.

Then, suddenly, I notice that Tessa is shredding a frond from one of the pot plants. Shit. There’s five-year-old intellectual curiosity for you.

‘Anyway, we must go,’ I say hastily. ‘We’ve taken up too much of your time. Thank you so much, Professor Russell.’

‘Please.’ He beams at me. ‘Do call me John.’

‘John.’

John leads us back through the house and we say goodbye with lots of warm hand-shaking and promises to have tea some time. As I’m opening our own front door, I’m so busy trying to picture him and Owen as gangly teenage boys that Tilda’s voice makes me jump.

‘Sylvie!’ She’s striding down the path, dressed in a rather dated maroon work suit, and beckons me over vigorously. ‘How’s things?’

‘Oh, hi!’ I greet her. ‘I’ve just been in Professor Russell’s garden. He’s really lovely. We should have drinks or something.’ I release Tessa’s hand. ‘Go and show Anna her plant, darling. And get your book bags. I’ll be there in a minute.’

‘So?’ Tilda’s eyes flash at me as Tessa scampers inside the house. ‘How was dessert al fresco? I haven’t had the full debrief yet.’

This is true. Apart from a thirty-second hello-thank-you-goodbye when we got back from the sculpture garden, I haven’t seen Tilda. She’s been working for one of her clients on site in his Andover office, so we’ve missed our morning walks. Which means she has no idea what’s been going on. I glance cautiously towards the house, but there’s no sign of Dan. Still, just to be sure, I pull the front door to.