On 7 November 1974, a nanny named Sandra Rivett was bludgeoned to death in a posh Belgravia basement. A second woman, Veronica, Countess of Lucan, was also attacked. The man named in court as perpetrator of these crimes, Richard John Bingham, 7th Earl of Lucan, disappeared next morning. The case, solved in the eyes of the law, has retained its fascination ever since. 40 years on, it is time for the definitive account. Laura Thompson, acclaimed biographer...