As we began to walk again our group broke up. Jonny went off on his own devices, his climbing clumsy. He loped along as a monkey might if finding itself on an unaccustomed perilous walkway, even to the extent of proceeding on all fours. His progress was quite swift, though, as he crossed the roof of 11 Russia Road and dropped down over its distant rim. The last we saw of him was his surly face. He didn’t wave. Wim remained with us, strolling rather than walking, never looking down at his feet. The obvious comparison is with a cat, and Wim on the roofs moved with the same casual elegance, the same to-the-manner-born negligence and unthinking ease, as Mabel on the tightrope edge of a balcony rail. The only concession he had made to discretion—after all, we none of us had any business to be up there on other people’s property—was to change his embroidered coat for a plain dark sweatshirt. His coil of rope he had slung over his shoulder the way a woman carries a bag with a long strap.

When we reached the end of the Russia Road roofs, the point where Jonny had disappeared, I saw that here was a change of configuration. Russia Road met Torrington Gardens at an acute angle. The streets themselves parted in a hairpin bend or triangle shape, the apex of which was a large house, a mansion I had often looked at from below. It had perhaps been built twenty years before the terraces it linked, it was Palladian to their late Victorian, its roof joined to theirs but some six feet lower on the Russia Road side and more like ten feet on Torrington Gardens. It was quite dark but still I could see that on the wall which was the end of the Torrington Gardens terrace a thoughtful builder had provided bands of stone on the brickwork, four of them, carved in a nailhead design and each about two feet apart, though no doubt for artistic reasons rather than for use as steps. This side presented no problem. There were two drainpipes on the wall, their snaky branches hung with ivy.

“It’s all flats, that house,” Silver explained. “Someone lives in the top flat. They’re probably out, they go out a lot in the evenings, but we’d better not take the risk. So don’t jump down.” How did he know about the people who lived there? He seemed to know everything about who lived where and their habits and routines. “We don’t really want them telling the police they keep hearing things that go bump in the night.”