But I flashed on the night that Billy Greene ruined his hands. I remembered the basement in a suburban house where we cornered a man called Ian Peck, far better known as Bob the Butcher, currently serving a life sentence for murder. I remembered that basement as a place of damp and dust and death, the black hole where my boss DCI Victor Mallory received a fatal knife wound to the neck.

It was very dark down there, one weak bare light bulb illuminating the horror, and even now I could feel the ache in my ribs beyond the dent in my Kevlar Stealth where Bob had tried to stab me. Bob was small but possessed with the simian power of the insane, and he took me out of the game almost immediately. But through the stars in my vision brought on by a blow to the back of the skull I watched PC Billy Greene throw himself into the flames of a barbecue pit for roasting human flesh.

It was a ragged hole that had been doused with petrol and a naked woman was screaming inside it, a journalist called Scarlet Bush who Bob had abducted, and I remembered the smell of burning flesh and what Billy had looked like in his hospital bed, his hands wrapped in oozing bandages, months of care ahead of him, his future uncertain. But what I remembered most of all was that he had never hesitated to throw himself into the flames.

‘I never think of you as a canteen cowboy, Billy,’ I said. ‘OK?’

‘OK. Thanks.’

‘Where were your new friends from?’

‘Vilnius and Budapest,’ he said, confirming what Steve Warboys had insisted. The women of the Champagne Room were all in the country legally. Give or take a dodgy student visa or two, they were even working more or less legally. The Champagne Room did not import its dancers in the back of a lorry. They didn’t need to. I heard Billy’s stomach rumble.

‘You want to stop for something to eat?’ I asked him.

‘My mum will have something waiting for me,’ he said. ‘Let’s just get back home, shall we?’

Going home was always fine by me. And it should have been an easy run. It should have been an hour cruising on the empty late-night motorways that snake through all that Essex countryside and then back home to London, dropping off Billy to his mum, who would be waiting up for him, and then to Smithfield, where Mrs Murphy and Stan would be dozing on the sofa.

But it didn’t work out like that.

The motorway miles drifted by and Billy and I had lapsed into silence until we saw the blue and red lights of trouble piercing the darkness somewhere ahead of us.

‘Looks like an accident,’ Billy said.