Less than an hour and a half later, he was seeing signs that said, ‘Highgate Wood’ and ‘West End’. It was five o’clock and starting to get dark. Great. Central London at rush hour. From a traffic point of view, it couldn’t have been worse. So resigned was Simon to his fate that he didn’t notice when Seed took a left turn ahead of him. He sped on past, then had to turn round. Seed had gone down a side street off Muswell Hill Road—something beginning with an ‘R’. Simon drove back past the entrance to Highgate Wood. Ruskington Road—that must have been it. He turned right. He’d got halfway down the road when he saw Seed walking towards him. He prepared to be seen—for the inevitable confrontation—but Seed didn’t notice him. He had his head down. Once he’d passed Simon’s car, Simon pulled in and watched Seed in his rear-view mirror. At the bottom of the street, Seed turned left.

Why had he chosen Ruskington Road? Simon wondered. Olivia, Charlie’s sister, used to live round here. She moved after her downstairs neighbour—and, by extension, the house they shared—appeared on a tacky daytime property programme. Simon could see Seed’s car parked a few metres ahead on the other side of the road, in front of number 23, a white-painted four-storey terrace that was divided into flats. Simon saw a light glowing behind the curtains in the basement window and another in the highest dormer window.

Did Seed know someone who lived in one of the flats? Or nearby?

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.