Regret begins to swell painfully in my chest, but there’s no time for it to properly take root, because as I stare wildly around the room, I suddenly realise: I know where I am.

This is Dalston. 79 Kingsland High Road, Dalston. The flat Harv and I rented together after we left uni.

I stagger out of bed, still trembling like mad, my eyes darting from one side of the room to the other. It’s all exactly as I remember it: the fire extinguisher slumped in the corner by the wardrobe, the laminated safety codes stuck to the back of the door, the horrible strip lighting on the ceiling that – when activated – gave everything in the room a sickly yellowish tint.

Both floors of the flat had previously been the offices of an Albanian law firm, but at some point the Albanian lawyers had given up trying to wage their legal battles over the constant roar of the London Overground, and the landlord had taken the opportunity to rebrand the place as a ‘bijou apartment space’. He’d not even bothered to redecorate – just squeezed in a couple of cheap single beds and a sofa, and left everything else as it was, right down to the jaundiced lighting and the fire safety accessories.

The room starts quivering again as another train bursts out from behind the building, making the window panes chatter like wind-up teeth.

If I remember rightly, Harv and I had allocated who got which bedroom by playing an extremely competitive game of FIFA, which he had won. Both rooms were ridiculously loud, but the one Harv chose, at the front of the flat, picked up only random, sporadic street sounds – the howl of a fox, the scream of a drunken argument, the glassy explosion of a car window. And Harv apparently preferred all that to the meticulously scheduled sleep deprivation of the back room – my room – which had the train tracks running literally right beside it.

We were in this flat for just over three years, and I don’t think I ever slept more than four hours consecutively in that whole time.

Which suddenly makes me wonder: what date have I landed on now? We lived here from, what … 2008 to 2011? So I might just have jumped five years in the blink of an eye.

The thought makes me drop weakly onto the edge of the bed.

My head is ringing with confusion, but I can’t exactly stay sitting in this room forever. I start getting dressed, picking up clothes at random from the floor. Harv’s bedroom door is shut, so I creep downstairs, nostalgia prodding me sharply with every footstep. I pass our boxy living room and spot the grimy fish tank next to the TV that contains two goldfish we named after members of the Wu-Tang Clan, though right now I can’t remember exactly which ones.