He stood and reached a hand across the coffee table and after a moment Eddie leant forward and shook it.

‘Right. Now let’s have a bit of that cake.’

Mum gave a little sigh of relief and reached for the knife.

And I did the best I could to smile, then hurriedly left the room.

There is a definite hierarchy to heartbreak. I worked it out. Top of the list is the death of the person you love. There is no situation likely to elicit more shock and outright sympathy: faces will fall, a caring hand reach out to squeeze your shoulder. Oh, God, I’m so sorry. After that it’s probably being left for someone else – the betrayal, the wickedness of the two people concerned bringing forth affirmations of outrage, of solidarity. Oh, that must have been such a shock for you. You could add forced separation, religious obstacles, serious illness. But We drifted apart because we were living on separate continents is, while true, unlikely to prompt more than a nod of acknowledgement, a pragmatic shrug of understanding. Yeah, these things happen.

I saw that reaction, albeit dressed up in maternal concern, in my mother’s response to my news, and then my father’s. Well, that’s an awful shame. But I suppose it’s not a huge surprise, and felt faintly stung in a way I couldn’t express – What do you mean not a huge surprise? I LOVED HIM.

Boxing Day slid by slowly, the hours turgid and sad. I slept fitfully, glad of the distraction that Eddie created so that I didn’t have to be the focus of attention. I lay in the bath and on the bed in the little box room, wiped away the odd tear and hoped nobody would notice. Mum brought me tea and tried not to talk too much about the radiant happiness of my sister.

And it was lovely to see. Or it would have been, had I not been so heartbroken. I watched the two of them surreptitiously holding hands under the table while Mum served supper, their heads bent together while they discussed something in a magazine, their feet touching as they watched television, Thom wedging his way between them with the confidence of the utterly loved, indifferent to who was doing the loving. Once we were past the huge surprise, it made perfect sense to me: Treena was so happy, relaxed in this woman’s company in a way I had never seen. Occasionally she would cast me fleeting glances that were shy and quietly triumphant, and I would smile back, hoping it didn’t look as fake as it felt.

Because all I felt was a second gigantic hole where my heart had been. Without the anger that had fuelled me for the past forty-eight hours I was a void. Sam had gone and I had as good as sent him away. To other people the end of my relationship might have been comprehensible, but to me it somehow made no sense at all.

On Boxing Day afternoon, as my family dozed on the sofa (I had forgotten how much time in our household was spent either discussing, eating or digesting food), I roused myself and walked to Stortfold Castle. It was empty, bar a brisk woman in a windcheater with her dog. She nodded hello in a way that suggested she wanted no part in any further conversation, and I made my way up the ramparts and onto a bench where I could look out over the maze and the southern half of Stortfold. I let the stiff breeze sting the tips of my ears and my feet grow cold, and I told myself that I wouldn’t always feel so sad. I let myself think about Will, and how many afternoons we had spent around this castle, and how I had survived his death, and I told myself firmly that this new pain was a lesser one: I was not facing months of sadness so deep it made me feel nauseous. I would not think about Sam. I would not think about him with that woman. I would not look at Facebook. I would return to my exciting, eventful, rich new life in New York, and once I was fully away from him, the parts of me that felt scorched, destroyed, would eventually heal. Perhaps we had not been the thing I’d thought we were. Perhaps the intensity of our first meeting – who could resist a paramedic after all? – had made us believe the intensity was ours. Maybe I had just needed someone to stop me grieving. Maybe it had been a rebound relationship and I would feel better sooner than I thought.

I told myself this over and over again, but some part of me stubbornly refused to listen. And finally, when I got tired of pretending it was all going to be fine, I closed my eyes, put my head into my hands and I cried. At an empty castle on a day when everyone else was at home, I let grief course through me, and I sobbed without inhibition or fear of discovery. I cried in a way that I couldn’t cry in the little house on Renfrew Road, and wouldn’t be able to once I got back to the Gopniks’, with anger and sadness, a kind of emotional bloodletting.

‘You fecker,’ I sobbed into my knees. ‘I was only gone three months …’

My voice sounded strange, strangled. And like Thom, who used to look at his own reflection deliberately when crying and then cry even harder, the sound of those words was so sad and horribly final that I made myself cry even harder. ‘Damn you, Sam. Damn you for making me think it was worth the risk.’

‘So can I sit down too, or is this, like, a private grief fest?’

My head shot up. In front of me stood Lily, wrapped in a huge black parka and a red scarf, her arms folded over her chest, looking as if she might have been standing there studying me for some time. She grinned, as if somehow the sight of me in my darkest hour was actually quite amusing, then waited while I pulled myself together.

‘Well, I guess I don’t need to ask what’s going on in your life,’ she said, and punched me hard in the arm.

‘How did you know I was here?’

‘I walked round to your house to say hi as I’ve been home from skiing two days and you haven’t even bothered to call.’

‘I’m sorry,’ I said. ‘It’s been …’

‘It’s been hard because you got dumped by Sexy Sam. Was it that blonde witch?’

I blew my nose and stared at her.

‘I had a few days in London before Christmas so I went to the ambulance station to say hi and she was there, hanging off him like some kind of human mildew.’

I sniffed. ‘You could tell.’

‘God, yes. I was going to warn you but then I thought, What’s the point? It’s not like you could do anything about it from New York. Ugh. Men are so stupid, though. How could he not see through that?’

‘Oh, Lily, I have missed you.’ I hadn’t known quite how much until that moment. Will’s daughter, in all her mercurial, teenage glory. She sat down beside me and I leant against her, as if she were the adult. We gazed into the distance. I could just make out Will’s home, Grantchester House.

‘I mean just because she’s pretty and has huge tits and one of those porny mouths that look like they’re all about the blowjobs –’

‘Okay, you can stop now.’

‘Anyway, I wouldn’t cry any more if I were you,’ she said sagely. ‘One, no man is worth it. Even Katy Perry will tell you that. But also your eyes go really, really small when you cry. Like, microdot kind of small.’

I couldn’t help but laugh.

She stood up and held out a hand. ‘C’mon. Let’s walk down to yours. There’s nowhere open on Boxing Day and Grandpa and Della and the Baby That Can Do No Wrong are doing my head in. I’ve got a whole twenty-four more hours to kill before Granny comes to pick me up. Ugh. Did you get snail trails on my jacket? You did! You are totally wiping that off.’

Over tea at our house, Lily filled me in on the news her emails hadn’t covered – how she loved her new school but hadn’t quite got to grips with the work as she was meant to. (‘Turns out missing loads of school does have an effect. Which is actually quite irritating on the adult I-told-you-so front.’) She enjoyed living with her grandmother so much that she felt able to bitch about her in the way that Lily did about people she truly loved – with humour and a kind of cheerful sarcasm. Granny was so unreasonable about her painting the walls of her room black. And she wouldn’t let her drive the car, even though Lily totally knew how to drive and just wanted to get ahead before she could start lessons.