Carlie Enoch Ivy Marshall Actor Richard Dixon Leo Cayman Actor Benedict Wolf Hari Singh Actor Andrew Hill Baggy Man Actor Martyn Ellis Albert Actor Nicholas Banks Derwent-Broxley Actor Nia Trussler Jones Gladys Roberts Actor Will Poulter Bobby Jones Actor Conleth Hill Dr Alwyn Thomas Actor Hugh Laurie Dr James Nicholson Actor, Director, Writer Lucy Boynton Lady Frances 'Frankie' Derwent Actor Jim Broadbent Actor Jonathan Jules Ralph 'Knocker' Beadon Actor Miles Jupp Henry Bassington-ffrench Actor Paul Whitehouse Landlord Actor Joshua James Dr George Arbuthnot Actor Maeve Dermody Moira Actor Morwenna Banks Mrs Cayman Actor Daniel Ings Roger Bassington-ffrench Actor Alistair Petrie Rev Richard Jones Actor Amy Nuttall Sylvia Basington-ffrench Actor Agatha Christie Writer Basi Akpabio Producer Claire Jones Producer Helen Ziegler Executive Producer Damien Timmer Executive Producer James Prichard Executive Producer Jonathan Karas Executive Producer