Glenn was a driving instructor for the Met. Mostly based at Hendon, the twenty specialist courses he taught included anti-hijack protection driving, tactical pursuit and containment, advanced car, advanced motorcycle, off-road, high-speed response and – Billy’s lesson – driving a heavy goods vehicle.

Glenn ushered Whitestone and me off the tarmac and on to the scrubby grass as Billy slammed on his brakes.

This end of the landing strip had a wide circle of tarmac, big enough for a light aircraft to make a complete turn before heading off to the hangars that had been falling down for the last thirty years. Billy was meant to be practising his turn on the circle but he came in too fast and executed his turn too abruptly. The three of us jumped back as the truck went up on its left wheels, hovering dramatically for a long sickening moment until the airborne side came down with the crash of ten tons of steel.

The lorry screeched to a halt.

Billy buzzed down the window and wiped the sweat from his face on this freezing cold day.

Glenn looked up at him and smiled.

‘Good,’ he said mildly. ‘The main mistake that people make when they first drive an HGV is that they go far too slow. You’re not making that mistake. But you’re still struggling with the dimensions of the thing, aren’t you?’

‘Sorry, sir,’ Billy said. ‘I—’

Glenn held up his hand. ‘You’re doing fine. But it’s not a squad car. It’s an ocean liner. Whatever you ask it to do, please give it plenty of warning. Now let’s go again.’

Billy nodded gamely and the truck took off, picking up speed as he headed for the far end of the landing strip. Glenn walked back towards us and exchanged a look with DCI Whitestone.

‘Any other candidates?’ Glenn said.

Whitestone indicated the truck roaring down the tarmac.

‘Billy is it,’ she said. Then she looked at me.

‘It seems possible that old man Warboys was running a long firm at the Champagne Room,’ I said. ‘If that’s the case, then it would have been in collusion with his late grandson, Steve Warboys, although I have no idea if they were partners or employer and employee.’

‘Why the element of doubt?’

‘It’s also possible that it wasn’t a long firm and that Steve Warboys was just lousy at business. The Champagne Room was mortgaged to the hilt and owed money to everyone. But it doesn’t necessarily follow that all the debt was criminal activity. It could be incompetence. I met Steve. He was no businessman.’

Whitestone laughed grimly.

‘But his grandfather invented the long firm,’ she said. ‘Sounds like Paul Warboys was topping up his pension. These old faces never change.’

‘I still can’t see him involved in people smuggling,’ I said.

Whitestone looked at me with something like anger.