Simon got out of his car, locked it and ran towards Muswell Hill Road. He was afraid he’d be too late, but when he turned the corner, he saw Seed’s broad-shouldered outline walking down the hill some distance ahead. Simon ran to catch him up. It didn’t take long, and Simon didn’t allow himself to get too close. As Seed passed each lamppost, the shoulder-patches of his black jacket shone under the artificial light. Simon patted his pockets. He’d forgotten his phone, left it on the passenger seat. Damn. Charlie would try and call him within the next half hour, he reckoned. He’d started to be able to anticipate when she was going to ring. He liked that: knowing what she was going to do.

Seed veered off the main road and down a footpath, also downhill. He wasn’t the only one. Most of the twenty-odd people between him and Simon went in that direction as well. It turned out to be a shortcut to Highgate tube station.

Seed went to stand at the back of the ticket queue. Simon ducked behind a van that was selling coffee, milkshakes and fruit juices. Once Seed had passed through the barrier, Simon flashed his badge at the fluorescent-jacketed woman standing behind the gate and said, ‘CID. Quickly.’ She let him through, eyes wide. Probably worried about bombs on the tube, Simon thought, but he didn’t have time to stop and reassure her.

There was only the Northern line, direction north or south. It had to be south, Simon thought, otherwise Seed would have driven all the way to his eventual destination. It was presumably as easy to park in High Barnet or Finchley as it was in the Highgate/Muswell Hill area. Simon couldn’t see Seed any more, so he had to hope he’d guessed right. Instead of going to stand on the southbound platform, he hung back, waiting for a train to come. When he heard one pulling in, he moved forward and walked briskly up the platform.

He spotted Seed in a huddle of people by one of the sets of doors. He knew the risk he was taking: Seed could turn round and see him at any moment, but so what? There was no law against going to London. Seed didn’t have to tell Simon what he was doing there and vice versa.