And then I spot him. Hmm. All right, he’s shorter than I imagined, but definitely still cute. And he’s meandering along, talking on the phone – probably some terribly busy and important investment banking call, which is why he isn’t rushing, because otherwise he’d get out of breath – and as he sees me he raises an arm in greeting, and ends the call.

‘Jess,’ Theo says, kissing me on the mouth. He smells of whisky and I realise in a second that he’s already more than a little bit drunk. His eyes are crossing slightly, and he’s swaying – and not just because we’re being buffeted by the wind. ‘Sorry I’m a bit late, got caught up in a – thing.’ His jaw is stubbled and he looks hollow-eyed and exhausted. ‘You look lovely.’

He starts walking up the gangway towards the boat, and I realise I’m still standing, half expecting him to take the arm of my now-sodden coat. I hurry after him.

‘I’ll take your coat, madam,’ says a man in a white jacket as we step onto the riverboat. He hands us each a black mask. Mine is trimmed with tiny diamante sparkles, which glitter in the light. Theo’s is plain black. He slips his on immediately and his eyes gleam out at me.

‘The ladies are just over there, if you want to—’ He gives me an up and down look, and I suddenly feel very not-London and a bit scruffy, then checks his phone. He catches a glimpse of someone over my shoulder and waves at them. ‘You nip to the loo, and I’ll get you a drink. Don’t forget your mask.’

A second later, he’s gone. I go to the bathroom and look at myself in the mirror, fixing my lipstick – which I’ve chewed off, biting my lip in anticipation and nerves waiting for him to arrive – and try to tame my hair, which has come loose in the wind and rain so that lots of dark tendrils are fluffing around the edges of my face. I hook the mask on and look at myself once more.

I feel excited, and glamorous, and I tell myself that this is all very romantic. Me, at a masked ball, in London, with an investment banker as my date. A slightly drunk one, but nonetheless.

I climb the stairs and realise that while I’ve been down there they’ve loosed the boat from its moorings, and we’re sailing. The floor is swaying slightly beneath my feet.

The space is thronging with people, and I stand for a moment, trying to work out which one of the hundred or so men in black tie and a plain black mask is Theo.

‘There you are,’ he says, over my shoulder. I turn around and he’s holding a bottle of expensive champagne with a glass already poured for me. He takes a slug from the bottle. ‘Thought you’d gone overboard.’