Did somebody say Belgravia? Surely not. The area has long been regarded as one of the most sterile postcodes in London, but the arrival of Gwynnie - her new neighbours include Lady Helen Windsor, Jimmy Choo CEO Tamara Mellon, Albert Finney and Tania Bryer - suggests that the once glamorous street, where in the Fifties the Countess of Mountbatten used to entertain on a lavish scale, is making a comeback.