We had turned off the great looping motorway that encircles the city and come down the long straight stretch that runs all the way to the lights of north London. Round midnight on most nights of the year, it is a strip of road much favoured by the boy racers of Essex. They speed here. They preen here. And too often they die here.

On the other side of the road, I could see the lights of the emergency services winking far ahead where the blackness of the country began to be lit by the orange sodium lights of the city. Blue for the law, red for the ambulances, and plenty of both. The traffic on that side of the road had begun to slow and thicken and as we got closer I saw the sickening sight of two cars crushed like cigarette packets by the side of the road.

I slowed the BMW X5 as we passed, close enough to see the expressions of the fire crews and paramedics and the police, their faces taut with shock, and as I pulled away, I saw jagged scraps of metal, careering skidmarks and, glinting like tossed diamonds, the crushed glass of the windscreens. A body bag was being zipped.

I put my foot down. Our side of the road was almost empty but on the other side, where the accident had happened, the traffic was slowing down. As we went faster, it was coming to a total stop. Motorists were getting out of their vehicles.

And then I saw the lorry.

It was stopped in the fast lane, the traffic stagnant both ahead and behind, perhaps five hundred metres from the accident.

The driver had not joined the other motorists who were stretching their legs and checking their phones. He stayed in the cab, but as we passed the lorry the back door of his vehicle came open.

And two men jumped out.

‘Max!’ said Billy Greene, looking back.

‘I see them,’ I said.

And I watched in my rear-view mirror as the men did the one thing that the guilty can always be guaranteed to do.

They ran like hell.

I pulled down hard on the steering wheel and did a U-turn up on to the central reservation, and suddenly we were heading in the other direction. The stalled traffic was too thick to allow us on the road and so I bumped along the frost-hardened grass at a teeth-jolting twenty miles an hour.

Half a mile ahead of me was the stopped lorry, getting closer every second. The back door was wide open now.

A head stuck out.

A young man emerged, sniffed the air and jumped to the ground. He stood for a moment in the fast lane of the motorway with nothing moving, looking warily at all the blue lights of all the authorities waiting ahead.

Then he made a dash for the hard shoulder and beyond.