The second son of Eric Llewellyn Newell, of High Lodge, Hadleigh, Suffolk,[2] an Oxford-educated physician who served as a captain in the Royal Army Medical Corps,[3] Newell was educated at Taunton School and completed his National Service, where a fellow recruit was Michael Caine, before training at the Royal Academy of Dramatic Art, alongside Albert Finney and Peter O'Toole.

[4] In an interview with the TV Times in 1968, he claimed to have gained weight as a deliberate attempt to boost his career, marking him out for some niche roles.

[4] He had previously appeared in two earlier Avengers episodes: "The Town of No Return" (Diana Rigg's debut) and, as a Minister of the Crown, in series five's "Something Nasty in the Nursery".

Other cult television appearances included roles in Maigret, The Persuaders!, Randall and Hopkirk (Deceased), the Doctor Who story "The Android Invasion", The Young Ones and Kinvig.

Later in life Newell succeeded in losing a substantial amount of weight, but this did not prevent his early death from a heart attack.