did the second actor take part in theatre plays?
Yes, in"The Scheming Lieutenant".
Peter Sallis
He made his first professional appearance on the London stage in September 1946 in a walk-on part in Richard Brinsley Sheridan's "The Scheming Lieutenant" (1775).

what is last of the summer wine? A British sitcom. was it made into a film? Yes,  "Getting Sam Home". when was the sitcom released? 1973 how many seasons did the sitcom have? UNANSWERABLE can you name some other sitcoms? "The Royle Family", "The Office", "Early Doors", and "Gavin & Stacey" which channel ran the original sitcom? BBC who were the actors of the sitcom? Bill Owen and Peter Sallis. did the first actor, act in other shows? UNANSWERABLE did he win any awards? UNANSWERABLE
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Peter Sallis [SEP] Theatre work
The show was a minor success and ran for six months in New York, opening at the Belasco Theater before transferring to the Shubert Theater. Sallis reprised his role in the 1968 film adaptation.