“There are two police cars down there. The two officers who’ve been at the door are going back to their car. They’re talking to someone inside. A chap’s getting out. He’s a guy about my own age, going bald, in a green jacket.”

Silver said, “The only thing for you to do is to go. Now. Get the money and your passports. Leave everything else.”

Down there, entering Torrington Gardens from the Peterborough Avenue end, a siren began to wail. It was a familiar noise but it sounded different, menacing, powerful, a real threat and therefore frightening. We couldn’t hear ourselves speak for the noise. As the wail died away on a series of short sharp cries, Andrew said, “Go where? Down into the street? Into the lion’s mouth, that would be.”

“We’ll go over the roofs,” Silver said.

Three minutes was about what we had. That was the time we calculated it would take them to summon Vivien Nyland to open the front door, come in, and climb the stairs. Andrew complied with Silver’s order but he argued all the time. The money he insisted on carrying himself. If he was caught he was afraid of being found with a false passport on him.

“I’ll carry all your passports,” I said, and no one disagreed. That’s how I happen to have them now, the three of them with their photographs and their false identities.

“Change your shoes,” Silver said to Alison. “Quick. Now.”

Jason was wearing the new trousers we had bought him. We had never noticed before that Alison always wore shoes with heels, most of them high. She had no flat shoes, no trainers, no walking shoes. I couldn’t imagine her on that mansard in pumps with two-inch heels. Both she and Andrew grabbed a coat. I pulled a sweater over Jason’s head. He was excited, full of enthusiasm at the idea of escaping his pursuers by a rooftop flight.

“We’ll go out of a back window,” Silver said. “If we try the front onto the balcony they’ll see us. This way we’ll be quite safe.”

Alison reached for one of the china birds, the greenfinch I think it was.

“Leave the bloody bird,” said Silver in a voice I’d never heard him use before. He went to the front door, opened it. A ghost of the twittering we had heard was coming from the flat below. Then, soon, came the clatter of Vivien Nyland’s shoes on the marble treads. Silver closed the door and shot both bolts. It would take additional minutes to break it down.