Initially, Watson was played by David Burke (who had earlier played the villain in an adaptation of "The Adventure of the Beryl Coronet" for the 1965 BBC series starring Douglas Wilmer and Nigel Stock). Burke appeared in the first series "Adventures" before leaving to join the Royal Shakespeare Company. He was replaced by Edward Hardwicke, (who had earlier had a role in an adaptation of "The Greek Interpreter" for the 1968 BBC series) who played Watson from the second series "Return" onwards.