Macdonald gazed out of the window, trying to work out where they were taking him. At some point they drove over the Thames, which meant they weren’t taking him to Belmarsh, but his restricted view meant that he had no clear idea of which direction they were heading.

Macdonald sensed they weren’t taking a direct route to the prison. That, and the armed escort, suggested the police believed he was an escape risk. He craned his neck and searched the sky for a helicopter, but saw nothing.

The sun was dropping towards the horizon so it must have been mid-afternoon when he saw the prison wall in the distance. There was no mistaking its nature: it was over thirty feet high and made of featureless brown concrete topped by a cylindrical structure like a large sewage pipe that ran its full length. There was no barbed wire, so presumably the cylinder was an anti-climbing device. If he was going to get out of the prison, Macdonald reflected, he wouldn’t be climbing over the wall.

The van slowed and Macdonald glimpsed a sign: HM Prison Shelton. Then it turned right and headed towards a gatehouse. A uniformed guard raised a barrier, and the van drove through, then stopped in front of a large gate. It rattled back and, a moment later, Macdonald saw three prison officers standing at a doorway, big men, with barrel chests and weight-lifters’ forearms, in short-sleeved white shirts with black epaulets. As the vehicle came to a stop another guard appeared, holding a large Alsatian on a tight leash.

The engine cut out. The Alsatian barked. The three guards folded their arms across their chests and waited. Macdonald heard footsteps outside his stall. A prison officer was standing in the doorway, in full uniform with a peaked cap. He undid the handcuff, took it off the rail, then fastened it to his own wrist. ‘Welcome to Shelton,’ he said, deadpan.

He nodded for Macdonald to stand up, then led him down the van and out into the courtyard. The Alsatian barked again, and struggled to get close to Macdonald, but his handler held him back. The prison officer took Macdonald through a door which led to a reception area. Off to the left there was a glass-walled holding cell lined with wooden benches, and to the right a waist-high desk of dark wood. A prison officer in shirtsleeves was standing behind a line of metal trays. He reached for a clipboard as Macdonald was brought in front of him. He took a form from one of the trays, picked up a pen and looked at Macdonald expectantly as the escorting officer removed the handcuff from his wrist. ‘This is the shooter,’ he said. ‘Be gentle with him.’

The officer behind the desk grunted. He was in his thirties with long sideburns and a drinker’s paunch that hung over his belt, like a late pregnancy. ‘Name?’ he asked Macdonald.

‘I’m not giving my name.’

The officer frowned. ‘What?’