‘He can’t speak it today. Just Lithuanian. Finding the body shook him up. The rest of the cleaning staff are down in the underground car park. We can’t let them go until we’ve had a word. My two DIs are down there – Detective Inspector Gane and Detective Inspector Whitestone. If you can give them a hand . . .’

‘Yes, sir,’ I said.

At the door of the banker’s office two uniformed officers had established an entry and exit corridor where they logged everyone who came and went from the crime scene. Two PCs, one male and one female, both young, both of them with dark red hair. They could have been brother and sister despite the fact that the woman was small and whippet-thin, and the man tall and gangly. From the state of them they had to be the officers who had answered the call.

The man – a boy, I thought, although he was in his mid-twenties and only a few years younger than me – looked on the verge of passing out. As I approached he leaned against the wall and choked back the urge to be sick. The woman – and she looked like a girl, despite the Metropolitan Police uniform – placed one small hand on her colleague’s shoulder.

She looked up at me as I signed out of the crime scene.

‘His first body, sir,’ she explained, almost apologetic. She hesitated for a moment. ‘Mine, too.’

She was dealing with it better than the boy. But both of their startled faces were wide open and frozen with shock, like children who had just come downstairs and found their pet dead in its cage, or seen through Santa’s disguise, and got their first real glimpse of this wicked world.

‘Breathe,’ I told him. I inhaled deeply through my nose, released it through my mouth with a controlled sigh. Showing him how to do it.

‘Sir,’ he said.

There were six lifts for the office workers and one, much larger and much dirtier, for the help. I took the stairs, thinking I might find gloves. Thirty flights. By the time I was halfway down I was starting to sweat but my breathing was still even.

I stopped at a sound in the stairwell, a hundred metres below.

Looking down, I glimpsed a blur of movement. There was the hint of a shadow and then a distant door slammed shut. I called out but there was no response and I took the final flights more slowly, stopping when I saw something written on the wall.

One word in black.

The shade of black that blood dries to.

P I G

Not taking my eyes from the three letters, I took out my phone and photographed the black word on the filthy wall. Then I went down the rest of the stairs, hearing a babble of voices now, rising up from below ground, the sound getting louder every second.