‘The older I get, the more inclined I am to say those three words: I don’t know,’ says Baroness Rendell of Babergh. She turns 80 this week, and seems milder in person than in her writing. In photographs, too, she looks a bit haughty and forbidding, with incredible Ming the Merciless eyebrows. But the door was opened by a smallish woman with a sandy helmet of hair, a quizzical expression and an illuminating smile that appears from nowhere and sends her features skywards. The mouth, the eyebrows, the hair — everything lifts, as though she has stuck her finger in a socket.She has written, she estimates, about 70 books: her output is catching up with her years. She continues to be heavily productive, churning out about two titles a year, rotating between the Inspector Wexford novels, the ‘psychological thrillers’ written under her pseudonym Barbara Vine, and the rest, published under her real name and also found under Crime.