Patrick Malahide Chief Inspector Roderick Alleyn Actor Belinda Lang Agatha Troy Actor William Simons Inspector Fox Actor Christopher Northey Barker Actor Ewen Bremner Walter McNabb Actor Dominic Snowdon Ruskin Actor Denis Lill Thomas Cartarette Actor Frederick Treves Sir Henry Lacklander Actor Jane Lapotaire Elspeth Cost Actor Sandy Welch Detective Constable Robinson Actor Barbara Jefford Constance Cartell Actor Will Keen Ludovic Actor Eleanor David Margaret Ballantyne Actor Patsy Byrne Mrs Mitchell Actor Tom Wilkinson Gerald Lacklander Actor Margaret Tyzack Emily Pride Actor Elizabeth Spriggs Lady Lacklander Actor Derek Benfield Alfred Belt Actor John Gielgud Percival Pyke Period Actor Martyn Friend Director John Woods Director Jim Goddard Director T.R. Bowen Writer Cyril Williams Writer Ken Jones Writer George Gallaccio Producer John Walker Cinematographer Bernard Ashby Film Editing Michael Methven Production Design Brian Willis Costume Design