In award-winning miniseries Chernobyl, about the 1986 nuclear disaster, he portrayed the Ukraine plant’s deputy chief engineer Anatoly Dyatlov as a tyrannical bully. He made detestable characters watchable, such as the butler Turton in Julian Fellowes’ Belgravia, whom, he said “weasels his way through the story”.
On the silver screen he played Guy Haines in 2008 Bond film Quantum Of Solace, and he appeared in Harry Potter And The Half-Blood Prince in 2009, playing wizard Eldred Worple who wants to write about Potter.
Ritter was born Simon Paul Adams into a Catholic family in Gravesend, Kent, to toolmaker Ken and secretary Joan.
He changed his name to Ritter after returning to Britain to find another Equity actor had his name.
He made his TV debut on The Bill in 1992 but his career was defined on the stage. Starting off in fringe theatre in London, he toured with the Royal Shakespeare Company and the National Theatre in the late 1990s and early 2000s.
He received a 2006 Olivier nomination for best supporting actor in Coram Boy and a Tony nomination for his part in Alan Ayckbourn’s The Norman Conquests.
He starred as John Major opposite Helen Mirren in Peter Morgan’s play The Audience at the Gielgud Theatre in 2013.
Ritter, who died of a brain tumour, is survived by his wife, Polly Radcliffe, and their sons Frank and Noah.