I considered showing him my warrant card but I didn’t want to risk him closing the door in our faces.

‘We’re here about the plumbing,’ I said.

‘Okay,’ he said and we trooped inside.

It was another double-width tunnel but this one had been converted into a club, complete with a professional-level light gantry over the dance floor and a bar that ran down one wall. We were far enough from the sound system to hold a conversation, which is why our shirtless friend had heard us banging on the door. We squelched our way through a dim area that seemed given over to sofas, chairs and snogging couples towards the dance floor which was heaving with clubbers, mostly white, dancing mostly in time to the music. There was a lot of furry legwarmers, Lycra shorts and halter tops fluorescing in the UV light. But for all the bare belly buttons and spray-on hot pants, I was getting a definite sixth-form disco vibe from the crowd. Probably because none of them seemed old enough to vote.

‘Somebody’s parents are away for the weekend,’ said Reynolds. ‘I feel overdressed.’

The crowd quickly parted as the clubbers realised that we weren’t the cabaret act.

‘Maybe you can find a change of clothes here,’ said Kumar.

‘I don’t think they’ve got anything in my size,’ said Agent Reynolds primly.

Three people covered in sewage will have a dampening effect on even the most ardent clubber and it wasn’t long before a ripple passed through the crowd and two young women stalked through the dancers towards us.

They weren’t identical twins but they were definitely sisters. Tall and slender, dark-skinned, narrow-faced, flat-nosed and with sly black eyes that pinked up at the corners. I could just about tell them apart. Olympia was a tad taller and broader of shoulder with her hair currently in a weave that cascaded expensively around her shoulders. Chelsea had a long neck, a narrower mouth than her sister and was sporting what I judged to be about thirty-six man-hours’ worth of twisted hair extensions. They were wearing identical hot pink knit mini-dresses that I know their mother wouldn’t have approved of – I kept my eyes on their faces.

‘You’d better have a really good reason for this,’ said Olympia, folding her arms.

‘Agent Reynolds, Sergeant Kumar, let me introduce the goddesses of Counter’s Creek and the River Westbourne,’ I said, and bowed for good measure. The girls shot me a poisonous look but I figured they owed me for that time they left me to sink or swim in the Thames.

‘You know we’re Olympia and Chelsea,’ said Chelsea.

‘Although,’ Olympia said to Kumar and Reynolds. ‘We are goddesses and expected to be treated as such.’

‘I could arrest you if you like,’ I said. ‘I mean, is there actually anyone down here who’s old enough to purchase alcohol?’