Derek Jacobi is having a bad hair day. “Oh, he butchered it,” wails the actor in mock despair. “It’s the worst haircut I’ve ever had.” Considering he is about to turn 84, there must be a fair few haircuts to choose from. The photographer and I reassure him that his snowy locks are rather dapper, and he seems instantly placated. “Do you think so? Oh, I take it all back then.” His voice is as soft and warm as butter melting on a crumpet, his manner sparkly and self-deprecating. When he is politely asked not to let his arm droop over the side of the chair while his picture is taken, he raises a hand in horror: “Was I being limp-wristed? We don’t want any of that!”