‘I work mainly for Special Branch,’ Izzard told Hepton. ‘Serious Crime, that sort of thing. You know, someone walks into a building society and shoots dead a teller. They capture the whole thing on camera, but the image is too blurred to be recognisable. I clean it up until it’s sharp from arsehole to breakfast time. Which reminds me …’ He looked at his watch, then turned to Sanders. ‘There’s an all-night caff, just up the road and turn right. You can’t miss it. There’ll be about a dozen cabs outside. It’s where the drivers go for their break. Get us, let’s think, something hot, a sausage sandwich, something like that. Plus some cold sandwiches for later, corned beef or salami. And tell Alfie, the man behind the counter, that Izzard says he’s to give you a flask of tea. Got that?’

Sanders looked devastated. He had been demoted to tea boy by a man if anything a year or two younger than himself, with straggly shoulder-length hair and a T-shirt advertising a heavy-metal band. This was the third blow of the evening.

Hepton’s first impression of Izzard had been similarly coloured by his youth – he looked no more than twenty-six or twenty-seven – and his clothing. He had a London accent, too, harshly grained, the sort of voice heard at market stalls and football matches. But there was no doubt that he had a certain swagger that told you not to muck him about or underestimate him.

He offered Sanders a five-pound note from a wad pulled from his jeans pocket, but Sanders shook his head and stumbled away, still shell-shocked. Izzard watched the door close behind him.

‘Stuck-up sod,’ he said. ‘I hate bloody SIS. Mind you, the other lot are no better. Give me Scotland Yard every time. Their heads aren’t in the clouds. A bit more down-to-earth, you know?’

Hepton nodded, unable to think of any reply. Izzard had brought them into a large warehouse of modern corrugated construction. There were crates neatly stacked against one of the high walls, but this was no ordinary warehouse. Much of the floor space was taken up by another, smaller building of more solid, prefabricated construction. Izzard went to the door of this smaller building and unlocked it. An alarm sounded, and he switched on the lights before finding another key on his heavy chain and turning it in the alarm box, cancelling the ringing. He looked satisfied. They were in a small antechamber. On another door was a numerical keypad and a tiny keyhole. Izzard pushed five digits and turned a slender key in the lock, and the door clicked open.

Inside this room, there was an air-conditioned chill. Izzard swung an arm around proudly. ‘The lab,’ he said.