Jones won a scholarship to the Rose Bruford Training College of Speech and Drama —where he shed his Midlands accent. He spent time in Lincoln rep before making his London debut in 1962 with the Royal Shakespeare Company (RSC), performing at the Arts Theatre in Afore Night Come . According to the theatre critic Michael Coveney , Jones was "immediately one of the ... [RSC's] most distinctive character actors". In 1963 he played Stanley in the Harold Pinter -directed revival of The Birthday Party in 1963, followed by Maxim Gorky 's play Lower Depths at the Aldwych Theatre in 1964. In 1964 he appeared as Cucurucu in the Peter Brook -directed production of Marat/Sade in a production that included Glenda Jackson , Ian Richardson and Patrick Magee . He reprised his role for the Broadway production, and again for the film version (1967).
He became more widely known to British audiences in 1968, after his appearance in the six-episode television series The Caesars , in which he played Claudius . For this role, he won the award for the "World's Best Television Actor of the Year" at the 1969 Monte-Carlo Television Festival .In 1970 he took the eponymous role in Charles Wood’s television film The Emergence Of Anthony Purdy Esquire Farmer’s Labourer, directed by Patrick Dromgoole for Harlech TV. Other television work included the 1968 BBC three-part adaptation of Cold Comfort Farm (he also appeared in the 1995 film adaptation), the 1978 series Pennies from Heaven and the ITV children's programme The Ghosts of Motley Hall (1976–1978).His cinema career developed, with support roles in the Cold War thriller Firefox playing an MI6 spy chief, and in the director David Lynch 's films The Elephant Man (1980), Dune (1984) and Wild at Heart (1990).[7] In the 1980s series, The District Nurse , he played the senior partner in a father-and-son medical practice in 1930s Wales, with the unrelated Nicholas Jones as his son.
In 1980 he appeared as Sir in Ronald Harwood 's play The Dresser , first in Manchester, then transferring to the London stage; he later reprised the role on BBC Radio 4 's The Monday Play in 1993. Coveney said of Jones in the role: "No subsequent performance in The Dresser – not Albert Finney in the 1983 film , nor Anthony Hopkins on television in 2015 , nor Ken Stott in the West End in 2016 – matched the rumbling thunder of Jones".Apart from a brief spell in 2001, Jones retired from stage work in the early 1990s.
Jones played the character Sandy Thomas in ITV's Emmerdale from 2005 to 2018, when he left the programme. He said he had been offered a contract extension but he declined as he felt it was the right time to move on.