When in 1982 BBC Television wanted to provide Tom Baker as Sherlock Holmes with a worthy Dr Watson, instead of settling for a bumbling and ineffectual dimwit, they chose Terence Rigby, who has died aged 71 of lung cancer. The resulting mini-series, The Hound of the Baskervilles, was more believable than usual, partly thanks to Rigby's subordinate thoughtfulness. And his air of possessing not always articulated depths was ideal for the plays of Harold Pinter.
Rigby was already a familiar face in British television mystery, thriller and police series. Three years previously, his rather anonymous but mildly intense face had appeared in four episodes of the TV version of John le Carré's Tinker, Tailor, Soldier, Spy, in which he played the Soviet-bloc expert Roy Bland. His films included Get Carter (1971) and Tomorrow Never Dies (1997).
Born and brought up in the Erdington district of Birmingham, Rigby had been keen on acting since childhood. He showed this when he was in the Boy Scouts, at grammar school and while he was doing his national service in the RAF. After he had started training to be a surveyor, he went unhappily into building work as a labourer until, through a friend, he met the actor Bernard Kilby, who advised him to try for Rada.
While he was there, Derek Salberg, of the Alexandra Theatre in Birmingham, gave him the part of a Nubian steward in the Agatha Christie play Death on the Nile, at £5 a week - his first professional appearance.
After two years at Rada, Rigby wrote to the actor and director Bernard Hepton at the Birmingham Repertory Company. A small role in Antony and Cleopatra was followed by She Stoops to Conquer; then he went to Hull for a production of the farce Caught Napping, staying for the season in 1962.
While trying to advance his career in London, Rigby got a job cleaning tables at the restaurant of the Royal Opera House, Covent Garden, for which he was paid in sandwiches, and graduated to running the artists' bar. He realised he needed an agent, and this led to a job in a touring production in Keswick. Then came Julius Caesar in Carlisle, and a Shakespeare festival in Sunderland, where he played Sir Toby Belch in Twelfth Night.
For the London production of Pickwick with Harry Secombe, which opened in 1963, Rigby was given three small parts - and was required to understudy 11 more. After he had appeared in John Osborne's Epitaph for George Dillon, he learned that the role of the boxer Joey was vacant in Peter Hall's production of Pinter's play The Homecoming for the Royal Shakespeare Company (1965). Rigby offered to audition by performing a section of the Osborne as if it had been written by Pinter - and got the job. He created another Pinter character, the thuggish manservant Briggs, in No Man's Land (1975), with John Gielgud and Ralph Richardson in London and New York. When he came to play the itinerant Davies in a 2003 production of Pinter's The Caretaker, always hopeful of getting to Sidcup to recover his papers, the Guardian's Michael Billington hailed him as "the Pinter actor par excellence".
Rigby's career in television mysteries and police dramas had started in 1963, in an episode of the ITV series No Hiding Place, and between 1964 and 1967 he had a number of parts in the BBC's Dixon of Dock Green.
It was a tribute to his all-purpose features that he was able to bridge the gap between the era of gentle George Dixon and the rougher one that followed, when the police could be seen as sharing some of the crooks' combative and deceitful attitudes. In 1968 he was in Z Cars, the series that showed the police as drivers of fast cars that took them nearer to criminals, if further away from the street-using public. When the series developed into Softy Softly, he remained as PC Snow.
Notable television appearances came as Stalin in Testimony (1988), Tony Palmer's account of the political difficulties of the composer Dmitri Shostakovich, and in Alan Plater's three Beiderbecke series (1985-88) and Our Friends in the North (1996). In 1998 Rigby re-located to New York, from where he undertook stage work, including plays by Edward Bond and Mike Leigh, and the Julia Roberts film Mona Lisa Smile (2003). As he put it, "I'm not a married chap - and I don't think my marital status is likely to change. So I'm free to be a travelling Gypsy."
· Terence Rigby, actor, born January 2 1937; died August 10 2008