I doubt very much you’d do this without testing it first either.

I lift everything – tub, computer, box – off the desk and on to the floor for extra stability. Then I pick up Alan Shearer carefully, encircling his midriff with my finger and thumb like the book says you should, and I lower him into the zinc tub where he scampers around, a bit confused, poor thing. Soon, though, he just sits still, cleaning his whiskers.

I tap super-carefully on the laptop’s keyboard: first all the letters written on the black box, then 1020300784, then all the rest of the digits.

That’s ten twenty on July 30th, 1984, at precisely this spot.

Then I press ‘enter’.

A row of figures scrolls up super-fast on the laptop screen, and something strange appears above the tin tub. The best way to describe it is like a huge, just-visible bubble. I saw a clown once at a school science day make these enormous soapy bubbles with a loop of string and it was a bit like that, but less … definite. I reach out nervously to touch it, and it doesn’t pop. It just sort of shimmers and wobbles slightly.

I am so caught up in looking at this that a few seconds tick by before the stupidity of what I have done dawns on me:

THE TIME MACHINE TRAVELS AS WELL.

In dad’s QuickTime film, the zinc bath disappeared along with the clock.

I’ll be sending a hamster in a metal tub through unknown dimensions of spacetime with heaven-only-knows what consequences, and no way of following unless I can somehow build a replica time machine, and at this stage I think that’s doubtful.

These thoughts take about two seconds, max, and by the time I’ve stopped thinking them, I have leapt through the bubble, into the tub, unplugging the laptop from the mains socket and gripping it so hard it might crack as I sit staring at the screen while the numbers continue to scroll up and then … just … stop.

And nothing happens.

Well, not nothing, exactly. But I have to be really careful in describing this, because there is no flash, no explosion, no whooshing noise, or wind, or electric shock, or searing white light or anything. There’s only a strange and brief blurring in front of my eyes, as if a huge invisible lens has passed in front of me. I’m still staring at the computer screen but at the edges of my vision things are out of place and I slowly take my eyes off the screen and look around.

I’m still in the bunker but it seems different.

1. Dad’s letters have gone from the desk.
2. So has the mouldy cup, and I check with my hands where it was, running my palm over the desktop.
3. A minute ago, that would have sent up a small cloud of dust, but now it’s clean.

But some things have appeared that weren’t there before.

1. On the desk is a half-eaten packet of biscuits
2. On the floor is a small heap of comic books – Spiderman and that sort of thing. They may have been there before, but I think I’d have noticed and they’re not the sort of thing my dad would have had.
3. On the wall is a dartboard with some tatty darts in it. Again, I think I’d have noticed this before.

Along the wall are the bunk beds, made up as before. There is a box next to one, marked ‘Dole Pineapple’ – had that been there before? I couldn’t be certain.

There’s a scratching noise coming from by my feet and there is Alan Shearer. I scoop him up in my hands.

“Hello, mate! You made it!” He twitches his nose at me and I shove him in the big front pocket of my coat, which I’m pretty certain is not recommended by Dr A. Borgström in Hamster Fancying For Beginners, but it’s not going to be for long. Behind me the steps lead up to the door as before, but instead of being old with blistered paint and rust marks, the door is fresh and smooth.

“So that’s time travel, then,” I say to Alan Shearer out loud. I check myself over: everything seems all right. I put my right foot out and touch the floor beyond the zinc tub like I’m testing the water in a swimming pool. Seems all right, and I’m about to make for the door when I turn back and look carefully at the laptop. This, I realise, will be crucial to getting me back and I’m nervous in case it’s damaged. Its screen is still on, which reassures me, and I turn for the steps and open the steel door.

Crouching, I come out where the stairs are, and the planks are replaced over the hole. I ease a couple of them to one side and climb up the steps into the garage.

Into a different world. Well, the same world, but a different time. You’ll get used to it. I did.