He crossed the threshold and entered a cavernous, brightly lit space with ductwork on the ceiling and exposed brick walls. The room was huge. The size of half a football pitch. There was an armoury at one end of the space, secured behind a separate steel door. Nearby was a row of computer terminals, a stack of handheld radios and mobile phones on charge. In another corner he saw an open wardrobe. Suits and athleisure gear and dresses hung from a clothes rack, along with four sets of courier overalls: bright-blue shirts with orange trim, matching baseball caps and dark trousers. Next to the wardrobe was a make-up station with a vanity mirror surrounded by LED lights, a wig stand, a make-up case with powders and liners and brushes. Bowman saw shoe racks filled with high heels, trainers, walking boots, leather brogues. There was a kitchen countertop to one side of the entrance, with a microwave, kettle, drip coffee maker, toaster, sink. Further along, there was a breakout area with a flat-screen TV, two sofas, a few armchairs. Bowman saw a snooker table, a dartboard. Lockers. A row of bunk beds with bags scattered across the floor.

Across the room, two figures in plain civvies stood hunched over a map. One of the guys was very short. Five-four or maybe five. The man next to him was at least six inches taller and dark-skinned, with close-cropped hair, like a black leather skullcap. They paid no attention to Bowman. As he looked on, a slightly built woman hurried over to her two colleagues. She was dressed in a pair of tight black jeans, blouse and dark blazer. She had a plain face, short dark hair and lips the colour of strawberries.

‘The rest of the team,’ Mallet said. ‘You’ll be introduced to them in a few minutes. In there.’

He pointed to a large structure in the middle of the floor space. At first glance it looked like a steel container. Six metres long and three wide, with corrugated metal sides. The kind of thing you saw stacked up on transport ships or freight trains. A metal door had been fitted to one of the longer panels, Bowman noted.

‘We call it the Shed,’ Mallet added. ‘It’s fully soundproofed and screened for bugs. That’s where we have our briefings.’

Bowman looked round in amazement. ‘How long has all this stuff been down here?’

‘Nine years. Since we first created the Cell.’

‘How many guys on the team?’

‘Six, including myself,’ said Mallet. ‘You’re the seventh. Two of the lads are on another job right now. Overseas posting.’