I don’t know how long I lay there in the darkness, nursing a really bad headache, before I noticed that water was pooling around my boots. I did a little kick and heard it sloshing around. Ever since I’d started hobnobbing with the Goddess of the Thames and her daughters I’d started taking a keen interest in the hidden hydrography of London. So it didn’t take me long to work out that the nearest river to me was the Tyburn. But from the lack of smell I figured that this water was more likely to be coming from a ruptured water main.

In 1940 sixty-five people died when a bomb ruptured water and sewer pipes which flooded Balham Tube station. I really wasn’t in a hurry to recreate that particular historical precedent.

I told myself that my little void was unlikely to fill very quickly and in fact there was no reason for me to think that the water level would reach any higher than my ankles. I found myself just about as convincing as you can imagine and I was considering whether to indulge in a bit more panicked screaming when I heard a noise above me.

It was a vibration in the concrete, sharp percussive sounds of metal on stone. I opened my mouth to shout but a shower of earth fell from the darkness and I had to turn my head and spit frantically to avoid choking. Bright sunlight struck me like a blow on the side of my face, fingers dug into my shoulders. There was swearing and grunting and laughter and I was yanked into the light and dumped on my back. I flopped around like a fish and flailed my arms around just because I could.

‘Watch it, he’s fucking possessed,’ said a man’s voice.

I stopped moving and lay on my side just getting my breathing under control.

I was lying on grass, which was a bit of a surprise, I could feel it against my cheek and the green smell was tickling my nose. Birdsong, shockingly loud, came from above me and I could hear a crowd, which was to be expected, and the lowing of cattle – which wasn’t.