Bates was born in Bristol, England. His parents were both psychiatrists, his mother was French and he was the great-great-grandson of French scientist Louis Pasteur. He held dual-nationality and was bilingual, and was educated at Trinity College Dublin. He read French there, before winning a scholarship to Yale Drama School. The course completed, Bates returned to Ireland to make his stage debut in Shaw’s You Never Can Tell at The Gate Theatre, Dublin, in 1963. A career in repertory theatre soon followed and the young actor gained experience in productions ranging from Hedda Gabler to raucous comedies.

He portrayed Caligula in the series The Caesars and alongside Cyd Hayman in a passionate French tale of murder and mystery – Crime of Passion series. After playing Thomas Culpeper in an episode of The Six Wives of Henry VIII (1970), he went on to star in the BBC drama series, Moonbase 3 (1973) and the long-running Poldark, in which he played villainous George Warleggan. The series ran for 29 episodes, starting in 1975. He also played communist Paul Vercors in the final season of the drama series Secret Army. Because of his French ancestry and dark looks, he was often chosen to play a Frenchman on television, as for instance in a second series episode of ITV comedy drama Turtle’s Progress. Bates also appeared in the television movie Minder on the Orient Express, again as a Frenchman.