Three minutes after Rupert Sackville’s taxi left Castle Street, two workmen strolled into Sweeting Street. Hi-visibility orange jackets and blue hard hats, they carried a toolbox and a short lightweight metal ladder. Opposite Sackville’s office, one took a few steps up then opened the electrical box mounted on the wall. His colleague handed him a small screwdriver. A couple of turns and the lights glowed into life.