It was almost dark. We had been walking for what felt like hours. No part of me was dry. Even if we did reach the top, we’d see nothing from it, and we’d only have to come down again, and really, what was the point?

Luis didn’t believe in GPS. He said that people had managed for millennia with just the stars and the sun, and Garmins were just another way of making us spend more money. In principle I agreed, but from where I stood, panting and cold on the side of this slippery slate mountain, all I wanted was an LCD screen to tell me where to go.

While he folded and unfolded the sodden map under the fading light of his head torch, I ran a quick inventory in my head. Batteries: none. Phone: flat. Dry socks: two pairs. Food: half a block of Kendall mint cake, three dried apricots, possibly an out of date cereal bar. Water: everywhere.

“Which way do you think it is?” I heard myself murmur gently, not wishing to irritate him further.

“I’m looking, I’m fucking looking aren’t I? You think you can do better?”

He threw the OS map at me and it unfolded in the air. The wind caught it and cartwheeled it, a ghostly polygon, into the shallow stream below us.

“Nice one,” I spat.

I scrambled down to try and peel it from where it lay, plastered down by the drizzle and the water’s quickening pace. It came up in sodden, ragged pieces, like scraps of stripped wallpaper.

“Now what?”

Suddenly an unearthly crash sounded. It must have come from the sky, but we felt it inside us. In the soles of our feet. It could have been the mountain, growling. Almost instantly, an electric flash sliced down from the purple sky. It left a trail that throbbed in my eyes at every blink.

“Luis, now what?” I repeated, trying to steady the quiver in my voice.

“Now, we run.”