It was darker here, and cooler; tall pines blocked out the sun and their shadows felt unfriendly. I realised that we had never penetrated so deep into the woodland before. It was unfamiliar, even slightly sinister. I shouted Jimmy’s name over and over again but my voice just echoed back, as though the trees were mocking me.

‘Jimmy, please. Where are you? Come back, for heaven’s sake. You’re frightening me.’

Minutes passed. I began to run. At another fork in the path I stopped and listened until my ears ached. My brother was rarely quiet, often panting or muttering to himself, and so clumsy that surely I’d be able to hear the thud of his footsteps or the crack of twigs under his feet? But there was nothing – only the creaking of the trees and the song of distant birds.

How could he have disappeared so completely in just a few minutes? My heart was thudding as I tried desperately to decide what to do. Go forward, or back to where I’d last seen him? Surely he couldn’t have got lost in such a short time?

In London there were always people to help. Mum had bought Jimmy an identity tag, which he used to wear on a leather lace round his neck, just in case. Now, I cursed myself for not being able to remember whether he was still using it, realising with a rising sense of panic that we had never got round to updating the address.

Would he be able to find his way home? How far did these woods stretch? Where did they end? I had absolutely no idea what dangers the countryside might hold.

And then I heard it: so soft as to be almost inaudible, but unmistakeably a man’s deep voice. ‘Hello, laddie. What’re you doing down here?’

I began to run in the direction of the voice, barely noticing how the branches scratched my arms and brambles tore at my bare legs. I stopped and listened some more, then called, ‘Jimmy, Jimmy?’

The man’s voice again: ‘Over ’ere, dearie.’

At last I emerged into a clearing and there, in front of a dilapidated wooden hut, was Jimmy. As he turned round and smiled, I almost cried with relief.

The hut was set high off the ground on iron wheels, with a stable door and an arched roof that projected forward over a raised porch reached by wooden steps, at the top of which stood Eli, with a beaming smile. Beside him, a camel-coloured mongrel with rough, scraggy fur snarled and bared a mouthful of sharp teeth, as though it might cheerfully tear me from limb from limb, given half a chance.