I should have cuffed him, but Nightingale was lying in the road behind me making wet breathing sounds. It was what they call a ‘sucking chest wound’, and they’re not being metaphorical in their description. There was an entry wound ten centimetres below Nightingale’s right shoulder, but at least when I gently rolled him on his side I couldn’t find an exit wound. My first-aid training was unequivocal about sucking chest wounds – every second you spend faffing around is another second that the London Ambulance Service hasn’t arrived.

I knew that the back-up teams couldn’t have heard the gunshot because they’d have been there already, and I’d blown my Airwave when I levitated the gunman off his feet. Then I remembered the silver whistle in the top pocket of my uniform jacket. I fumbled it out, put it in my mouth and blew as hard as I could.

A police whistle on Bow Street. For a moment I felt a connection, like a vestigium, with the night, the streets, the whistle and the smell of blood and my own fear, with all the other uniforms of London down the ages who wondered what the hell they were doing out so late. Or it could just have been me panicking; it’s an easy mistake to make.

Nightingale’s breath started to falter.

‘Keep breathing,’ I said. ‘It’s a habit you don’t want to break.’

I heard sirens coming closer – it was a beautiful sound.

The trouble with the old boy network is you can never really be sure whether it’s switched on or not, and whether it’s operating in your interest or some other old boy’s. I began to suspect that it wasn’t operating in my interest when they brought a cup of coffee and a biscuit to the interview room. Fellow police officers being interviewed in a friendly manner get to go to the canteen and fetch their own coffee. You only get room service when you’re a suspect. I was back in Charing Cross nick, so it wasn’t as if I didn’t know the way to the canteen.

Inspector Nightingale was still alive, they told me that much before they sat me down on the wrong side of the interview table, and had been taken to the brand new trauma centre at UCH listed as ‘stable’, a term which covered a multitude of sins.