‘Well. I suppose that’s true.’ He considers this, looks sideways at me. ‘Four a day, uh?’

‘Sometimes more. Now, if you wouldn’t mind, I really have to get back. It’s not good for me to be seen coming out of the men’s loos too often.’

He smiles, and for a minute I can see how he might be in other circumstances. A naturally ebullient man. A cheerful man. A man at the top of his game of continentally manufactured car parts. ‘You know, I think I hear them calling your flight.’

‘You reckon I’ll be okay?’

‘You’ll be okay. It’s a very safe airline. And it’s just a couple of hours out of your life. Look, the SK491 landed five minutes ago. As you walk to your departure gate, you’ll see the air stewards and stewardesses coming through on their way home and you’ll see them all chatting and laughing. For them, getting on these flights is pretty much like getting on a bus. Some of them do it two, three, four times a day. And they’re not stupid. If it wasn’t safe, they wouldn’t get on, would they?’

‘Like getting on a bus,’ he repeats.

‘Probably an awful lot safer.’

‘Well, that’s for sure.’ He raises his eyebrows. ‘Lot of idiots on the road.’

I nod.

He straightens his tie. ‘And it’s a big job.’

‘Shame to miss out on it, for such a small thing. You’ll be fine once you get used to being up there again.’

‘Maybe I will. Thank you …’

‘Louisa,’ I say.

‘Thank you, Louisa. You’re a very kind girl.’ He looks at me speculatively. ‘I don’t suppose … you’d … like to go for a drink some time?’

‘I think I hear them calling your flight, sir,’ I say, and I open the door to allow him to pass through.

He nods, to cover his embarrassment, makes a fuss of patting his pockets. ‘Right. Sure. Well … off I go, then.’

‘Enjoy those brackets.’

It’s two minutes after he has left that I discover he has been sick all over cubicle three.

I arrive home at a quarter past one and let myself into the silent flat. I change into my pyjama bottoms and a hooded sweatshirt, then open the fridge, pull out a bottle of white and pour a glass. It is lip-pursingly sour. I study the label and realize I must have opened it the previous night, then forgotten to put the top on the bottle, and decide it’s never a good idea to think about these things too hard. I slump into a chair with it.

On the mantelpiece there are two cards. One is from my parents, wishing me a happy birthday. That ‘best wishes’ from Mum is as piercing as any stab wound. The other is from my sister, suggesting she and Thom come down for the weekend. It is six months old. Two voicemails on my phone, one from the dentist. One not.

Hi, Louisa. It’s Jared here. We met in the Dirty Duck? Well, we hooked up [muffled, awkward laugh]. It was just … you know … I enjoyed it. Thought maybe we could do it again? You’ve got my digits …

When there is nothing left in the bottle, I consider buying another, but I don’t want to go out again. I don’t want Samir at the twenty-four-hour grocery to make one of his jokes about my endless bottles of Pinot Grigio. I don’t want to have to talk to anyone. I am suddenly bone-weary, but it is the kind of head-buzzing exhaustion that tells me if I go to bed I won’t sleep. I think briefly about Jared and that he had oddly shaped fingernails. Am I bothered about oddly shaped fingernails? I stare at the bare walls of the living room and realize suddenly that what I actually need is air. I really need air. I open the hall window and climb unsteadily up the fire escape until I am on the roof.

The first time I came up, nine months previously, the estate agent showed me how the previous tenants had made a small terrace garden up there, dotting around a few lead planters and a small bench. ‘It’s not officially yours, obviously,’ he’d said, ‘but yours is the only flat with direct access to it. I think it’s pretty nice. You could even have a party up here!’ I had gazed at him, wondering if I really looked like the kind of person who held parties.

The plants have long since withered and died. I am apparently not very good at looking after things. Now I stand on the roof, staring out at London’s winking darkness below. Around me a million people are living, breathing, eating, arguing. A million lives completely divorced from mine. It is a strange sort of peace.

The sodium lights glitter as the sounds of the city filter up into the night air, engines revving, doors slamming. Several miles south, the distant brutalist thump of a police helicopter, its beam scanning the dark for some vanished miscreant in a local park. Somewhere in the distance a siren. Always a siren. ‘Won’t take much to make this feel like home,’ the estate agent had said. I had almost laughed. The city feels as alien to me as it always has. But, then, everywhere does, these days.

I hesitate, then take a step out onto the parapet, my arms lifted out to the side, a slightly drunken tightrope walker. One foot in front of the other, edging along the concrete, the breeze making the hairs on my outstretched arms prickle. When I first moved down here, when it all hit me hardest, I would sometimes dare myself to walk from one end to the other of my block. When I reached the other end I would laugh into the night air. You see? I’m here – staying alive – right out on the edge. I’m doing what you told me!

It has become a secret habit, me, the city skyline, the comfort of the dark, the anonymity, and the knowledge that up here nobody knows who I am. I lift my head, feeling the night breezes, hearing laughter below, the muffled smash of a bottle breaking, the traffic snaking up towards the city, seeing the endless red stream of tail-lights, an automotive blood supply. Only the hours between three and five a.m. are relatively peaceful, the drunks having collapsed into bed, the restaurant chefs having peeled off their whites, the pubs having barred their doors. The silence of those hours is interrupted only sporadically, by the night tankers, the opening up of the Jewish bakery along the street, the soft thump of the newspaper delivery vans dropping their paper bales. I know the subtlest movements of the city because I no longer sleep.

Somewhere down there a lock-in is going on in the White Horse, full of hipsters and East-Enders, and a couple are arguing outside, and across the city the general hospital is picking up the pieces of the sick and the injured and those who have just about scraped through another day. Up here is just the air, the dark and somewhere the FedEx freight flight from LHR to Beijing, and countless travellers, like Mr Scotch Drinker, on their way to somewhere new.