My earliest memory isn’t of an event. It’s a nightmare. (The symbolism didn’t hit me for quite a few years.)

I’m three years old, maybe four. I’m in a large, unfamiliar house. The sun is streaming in through the windows and I’m playing boisterous games with other children – there must be 20 or 30 of us, and no grown-ups to spoil the fun. But the house abruptly falls quiet when one of the girls cries out: “Can anyone else hear that?”

We listen. Sure enough, ever so faint, but unmistakeable: thump, thump, thump. The room grows dark as a cloud passes over the sun.

“What is it?” asks one boy. We look searchingly at one another, but no one steps forward.

I know what it is. Or rather, who it is. It’s Big Frog and his army of grisly, murderous monsters, and they’re coming to kill us all.

Big Frog is my nemesis. Although he’s a frog, he walks upright. He’s green and slimy and eight feet tall, and he marches at the head of a horde of the foulest, most hideous creatures you could imagine. His favourite snack is children. And his favourite flavour is ginger.

We all know instinctively that we can’t leave the house; they’ll catch us before we can reach safety. Our only hope of survival is to hide.

At this point, a disembodied voice – my mother’s, perhaps – rings out through the house, counting down from 50. So 30 children begin the most important game of hide and seek of their short lives.

Things are orderly to begin with – the thump is still distant, the monsters some way off – but become more frantic as the countdown progresses.

I start looking for a hiding place with two friends. We run to the upstairs bathroom, where we see a couple of kids crouching under a shelf, in plain sight. We’re certainly not going to join them.

“38. 37. 36…”

Next, the bedroom. Two children are crawling under the bed; I try to join them, but there’s no room.

“29. 28. 27…”

My remaining two friends and I race downstairs to the kitchen. They climb inside a cupboard. I plead with them to find somewhere better – it’s the first place the monsters will look – but they wedge themselves in and slam the door.

“17. 16. 15…”

The thumping noise is deafening now. Another two kids dive into the wendy house. I am the only one left who hasn’t managed to conceal himself.

“10. 9. 8…”

Despairing of finding a good hiding place, I hurry back to try to squeeze into one of the bad ones. But when I look under the shelf in the bathroom, I find that the children who hid there have turned to stone. It’s the same under the bed, in the kitchen, in the wendy house. They are all, I now notice, in pairs: one boy, one girl. They’re all safe. They’re all dead.

“3. 2… ONE.”

As the countdown reaches zero, the wall of the house caves in. I wheel round to face my doom alone.