Television and stage actor, James Hazeldine, best known for his roles in the hit series, London's Burning (1988-1995) and The Omega Factor (1979), has died suddenly at the age of 55.

Hazeldine, who played ''Bayleaf'' in the popular firefighters' series, had just opened in Christopher Hampton's new play at London's National Theatre, The Talking Cure, playing Freud opposite Ralph Fiennes's Jung, when he was taken ill last week with chest pains. Despite several days in intensive care, he died on Tuesday.

An actor of rare sensitivity and, as he showed last year playing the flawed Joe Keller in Arthur Miller's All My Sons at the National, of smouldering fire, Hazeldine's success, as so often, resulted from a solid theatre grounding. From humble beginnings - he was born in 1948, the son of a Salford dustman - he started out as an acting ASM (assistant stage manager). His initial aim, he revealed in an interview, inspired by the American film director, Elia Kazan, was, however, to be a director. At 11, he confided, he once saw Kazan's East of Eden, nine times in a week.

None the less, by the age of 15 he was apprenticed to Salford Rep as a student actor, having read that his idol had also once been a stage manager and actor. Between 1963 and 1968 he played seasons at Newcastle, Liverpool, and Manchester reps. In 1968, at the age of 20, he moved to London, working as an understudy at the Royal Court in the Edward Bond season. Crucially, there, he came under the wing of the influential writer and director Peter Gill. In 1969 Gill cast him in his Over Gardens Out, again in 1976 for his new play, Small Change, and in its revival in 1983 in the National's double-bill with Kick for Touch.

With his strong features and mop of black curly hair, Hazeldine should have made the perfect romantic hero. But his attempt at Troilus in the RSC's 1981 London season at the Aldwych earned what he later considered his worst review. He went on, however, to play the visionary poet, John Clare, in Bond's The Fool and Alcibiades in Timon of Athens with distinction.

By then he was well on his way, having broadened his range with a variety of television and film roles, from Frank Barraclough in the 1973 series, Sam, to Tom Crane, the journalist with - pre-The X-files - psychic abilities in the spy-parapsychology-thriller BBC Scotland series, The Omega Factor (1979). He was also the lover in the film, Pink Floyd, The Wall (1982). Among some of the other popular series in which he appeared were Inspector Morse (in which he played Digby Tuckerman), Agatha Christie's Miss Marple, Truckers, Young, Gifted and Broke, Chocky, and Corsican Brothers.

But it was Mike ''Bayleaf'' Wilson, member of Blue Watch B25, Blackwall fire-fighting crew that established Hazeldine's national popularity. And in more recent times, as the curls became flecked with grey, that innate integrity yet steely lightness were put to good use in Dalziel and Pascoe, Adrian Mole: The Cappuccino Years (as Ivan Braithwaite, opposite Alison Steadman) and this year as DI Stan Egerton in Mike Eaton's controversial television play, Shipman, with James Bolam.

In 1997, back at the National, Hazeldine brought a surprising complexity to his square-bashing Corporal Hill in Arnold Wesker's Chips with Everything. He was praised as ''the most rounded person onstage'', ''each dismissive look a low blow to the men's shrivelling self-esteem''.

In 1998 he returned to New York, playing bar-owning Harry Hope in the transfer of the Almeida's award-winning revival of Eugene O'Neill's The Iceman Cometh, with Kevin Spacey. Hazeldine had made his debut on Broadway in 1984 with Glenda Jackson in another O'Neill play, Strange Interlude. This week Jackson paid tribute to her co-star, calling his death ''tragic'', while Trevor Nunn, the NT's outgoing head, commented on the rarity of finding ''charismatic talent and selfless warm generosity'' in the same person. ''But this was so with Jimmy Hazeldine.''

An LWT spokesman probably spoke for many: ''As Mike 'Bayleaf', he was one of the most popular and best-loved characters. He will be hugely missed by everyone who had the pleasure to work with him.''

Hazeltine married in 1971. He leaves a wife, Rebecca, a son, Sam, and a daughter, Chloe. His part in The Talking Cure has been taken by Scottish actor Bill Paterson.

James Hazeldine: born Salford 1948, died London, December 17, 2002.