Deep in the basement of the British embassy in Budapest is a long, narrow corridor. Just before it ends, in a stockroom, the corridor turns sharply. On either side of the bend two large mirrors are mounted on the wall. Their glass has lost its sheen and the silver backing is cracked and faded. This is a haunted place. During the Second World War the building – then the Hazai bank – was home to part of the Swedish diplomat Raoul Wallenberg’s resistance operation. The mirrors had been positioned so that the guards could keep watch on the length of the corridor before intruders walked around the bend.