She is destined to be Britain’s first black marchioness — but Emma McQuiston will need all the charm and finesse of a diplomat to repair the relationship between her future husband Viscount Weymouth and his father, the Marquess of Bath. Chef Emma, 27, will marry Ceawlin Thynn in June at the orangery of the family’s 10,000-acre Longleat House in Wiltshire, where father and son now live in separate wings and, I am told, have not spoken to each other since last summer. Ceawlin, 38, was handed the responsibility of running the estate, including its safari park, more than six years ago. But Bath, 81 next month, and his son became estranged last year after Ceawlin decided that his father Alexander’s life work — erotic murals which cover many of the internal walls of Longleat — had to be removed. According to one of Bath’s ‘wifelets’, father and son have not spoken since August. ‘It’s terribly sad. They live in totally separate parts of house but now neither makes any effort to speak to the