Simon Lack had a small role in the opening episode of the second season of The Rivals of Sherlock Holmes: The Mysterious Death on the Underground Railway, in 1973.
I had thought that the detective was going to be The Old Man in the Corner, because Polly Burton is a reporter who always goes to a certain teashop to discuss cases with him.
But in this filmed version, Polly is an aspiring reporter who also works as the assistant for her uncle, Sir Arthur - a criminal lawyer.She also dates a police sergeant.
Sir Arthur is played by John Savident. His schtick is that he's always eating candy.
Polly Burton was played by Judy Geeson.
Her police boyfriend, Richard Frobisher, was played by Richard Beckinsale.
Among the other players, Anthony Higgins - a very young Anthony Higgins, played William Hazeldene, and Simon was Andrew Campbell.
Christopher Timothy - very small role
Lois Baxter and Anthony Higgins.
Supposedly, Lois Baxter played Madame Lamia in Doctor Who: "The Androids of Tara," according to the IMDB, but frankly she looks different in both roles...I pride myself on being able to recognize actors but she looks totally different as Madame Lamia.
The rest of the screen caps are of Simon Lack as Andrew Campbell. He's in the first scene, as a man in the train who sees the soon-to-be-murdered woman and a man (whom we never see) talking, then at the trial he identifies Sir Arthur's client as the man...only to be revealed as totally unreliable by Sir Arthur under cross examination.