The water was above the halfway point and running faster than a mountain stream. In case you’re wondering, I’ve kayaked down a mountain stream – it was a school trip and I spent a lot of time underwater. As the guy at the front I was doing that again now – only the water wasn’t as clean. In the absolute black, Kumar’s glowstick didn’t do much more than texture the darkness and add to the sensation that we were hurtling out of control.

‘Oh great,’ I screamed. ‘Now we’re a bobsleigh team.’

‘It’s the luge,’ yelled Kumar. ‘It’s only a bobsleigh if you’ve got a bobsleigh.’

‘You two are insane,’ shouted Reynolds. ‘There’s no such thing as a triple luge.’

Between duckings I glimpsed a patch of grey. I opened my mouth to yell ‘Daylight’ and then really wished I hadn’t when I got a mouthful of diluted sewage.

It was another intersection. I saw an alcove with a ladder and lunged – only to be swept past, with my fingers centimetres from the metal. My foot hit something underwater hard enough to pitch me over and the world’s first-ever Anglo-American Olympic sewer luge team broke up.

I slammed into another thing that was at least vertical and made of metal, and then something else caught hold of my ankle.

‘Are you holding onto me?’ I shouted.

‘Yes,’ gasped Reynolds. ‘And Kumar’s holding onto me.’

‘Good,’ I said. ‘Because I think I’ve found a ladder.’

20. Holland Park

20

Holland Park

The thing about absolute darkness is that you end up doing things very carefully, especially after the first time you nearly brain yourself on a concrete cross-beam. So when I reached the top of the ladder I felt around myself slowly – I had come up through another floor hatch, I thought. There were no lights visible in any direction.

I made a werelight, which revealed a rectangular concrete room with a high ceiling and a shadowy doorway at the far end.

‘I can see a light,’ said Reynolds from below.

‘Just a moment,’ I said.

I fixed the werelight to the ceiling with scindare in the hope that Reynolds would mistake it for a light fixture, and climbed out of the hatchway onto the gritty cement floor, freeing it up for her.

‘About time,’ said Reynolds.

I reached down to help her up. She was shivering and her hands were freezing. She crawled clear of the hatchway and flopped over onto her back breathing heavily. Kumar followed her up, staggered a few steps, and sat down heavily.

‘A light,’ said Reynolds, staring at the ceiling. ‘Thank God.’

We could still hear the water rushing away below us.