Claire Foy Margaret Campbell, Duchess of Argyll Actor Paul Bettany Ian Campbell, Duke of Argyll Actor Julia Davis Maureen, Marchioness of Dufferin and Ava Actor Camilla Rutherford Diana Napier Actor Sophia Myles Louise `Oui Oui' Campbell Actor Richard McCabe George Whigham Actor Sophie Ward Janet Kidd Actor Miles Jupp Dr Ivor Griffiths Actor Timothy Renouf Peter Combe Actor Sarah Phelps Writer Anne Sewitsky Director Chris Ballantyne Producer