‘There’s just something off about this job,’ she said. ‘I figured I’d rather have you check it now than have to call you in later.’

Like after breakfast, when I was awake, I didn’t say. You don’t. Not when going out all hours is practically the working definition of a police officer’s job.

‘I’ve got nothing,’ I said.

‘Couldn’t you—’ Stephanopoulos gave a little wave with her hand. We don’t generally explain how we do things to the rest of the Met – apart from anything else because we make most of our procedures up as we go along. As a result senior officers like Stephanopoulos know we do something but they’re not really sure what it is.

I stepped away from the body and the waiting forensics types swarmed past me to finish processing the scene.

‘Who is he?’ I asked.

‘We don’t know yet,’ said Stephanopoulos. ‘Single stab wound to the lower back and the blood trail leads back into the tunnel. We can’t tell whether he was dragged or staggered up here himself.’

I looked down the tunnel. Cut-and-cover tunnels have their tracks running side by side, just like an outdoor railway, which meant that both tracks would have to stay shut down while they were searched.

‘Which direction is that?’ I asked. I’d got turned around somewhere back on the mezzanine level.

‘Eastbound,’ said Stephanopoulos. Back towards the Euston and King’s Cross. ‘And it’s worse than that.’ She pointed down the tunnel where it curved to the left. ‘Just past the curve is the junction with the District and Hammersmith so we’re going have to close down the whole interchange.’

‘Transport for London’s going to love that,’ I said.

Stephanopoulos barked a short laugh. ‘They’re already loving it,’ she said.

The tube was due to reopen in less than three hours for the day’s normal service and if the tracks at Baker Street were closed then the whole system was going to seize up on the opening Monday of the last shopping week before Christmas.

Stephanopoulos was right though, – there was something off about the scene. More than just a dead guy. When I glanced up the tunnel I got a flash, not of vestigia but of something older, that instinct we all inherit from the evolutionary gap between coming out of the trees and inventing the big stick. From when we were just a bunch of skinny bipedal apes in a world full of apex predators. Back when we were lunch on legs. The warning that tells you that something is watching you.

‘Want me to have a look down the tunnel?’ I asked.

‘I thought you’d never ask,’ said Stephanopoulos.