Richard Griffiths, the nimble British character actor best known to American audiences as cantankerous, wizard-fearing Uncle Vernon in the blockbuster Harry Potter films, died Thursday at a hospital in Coventry, England. He was 65.

The cause was complications from heart surgery, his agent, Simon Beresford, told British media.

A veteran of the Royal Shakespeare Company, Griffiths was a man of impressive girth whose rotundity belied the physical and emotional deftness that characterized his best performances on stage and screen.

He won a Tony for his portrayal of an eccentric prep-school teacher with a terrible flaw in the 2006 Broadway production of Alan Bennett's play "The History Boys." He also starred in the movie version released the same year.

Last year he co-starred with Danny DeVito in the London revival of Neil Simon's "The Sunshine Boys" and was set to reprise his role as an aging comedian this fall at the Ahmanson Theatre in Los Angeles.

"He was an extraordinary actor," Nicholas Hytner, who directed Griffiths in "The History Boys," told BBC News on Friday. "He was able to be funny, sometimes hilariously funny, and desperately tragic ... at the same time. Very few actors have that."

In Britain, Griffiths attained cult popularity as Monty, the lascivious gay uncle in the 1987 black comedy "Withnail and I," ranked by the British Film Institute as one of the 100 greatest British films of the 20th century.

His portrayal of Harry Potter's uncle, Vernon Dursley, in whose house Potter lives when he is not studying wizarding at Hogwarts, introduced the celebrated British actor to a younger generation of moviegoers.

Daniel Radcliffe, who played Harry Potter and also co-starred with Griffiths in a 2008 Broadway production of "Equus," remembered his fellow actor as a generous mentor.

"Richard was by my side during two of the most important moments of my career," Radcliffe said in a statement Friday.

"In August 2000, before official production had even begun on 'Potter,' we filmed a shot outside the Dursleys' (house), which was my first ever shot as Harry. I was nervous and he made me feel at ease. Seven years later, we embarked on 'Equus' together. It was my first time doing a play but ... his encouragement, tutelage and humor made it a joy."

Griffiths was famous for his rambling, screamingly funny anecdotes. "Sometimes he would hold up shooting on 'Harry Potter' so that he could finish a joke," actress Fiona Shaw, who played Petunia Dursley in the movies, said Friday. "He was a philosopher clown."

Born on July 31, 1947, in the North Yorkshire town of Thornaby-on-Tees, Griffiths described his childhood as miserable: He was obese, a condition brought on by incorrect treatment of a glandular condition, and his parents were profoundly deaf and mute.

"I was big and fat and had weird parents," Griffiths told Britain's Independent newspaper in 2011.

Not until much later did Griffiths recognize the silver lining in his difficult upbringing. "My father taught me things about body language that psychologists have been catching up with ever since. He always knew when I was lying," Griffiths said in the Independent in 1997, "because my posture was all wrong."

After studying at the Manchester Polytechnic School of Drama, Griffiths was invited to join the Royal Shakespeare Company by artistic director Trevor Nunn in 1975. Among the roles he played over the next decade were Henry VIII, Falstaff and Bottom from "A Midsummer Night's Dream."

In the 1980s he began to land supporting roles in sweeping historical dramas, including "Gandhi," "Chariots of Fire" and "The French Lieutenant's Woman."

He was married for more than 30 years to Heather Gibson, whom he met in the early 1970s when they both worked in Northern Ireland for the Belfast Arts Theater company. She survives him.

Griffiths' breakthrough came as Uncle Monty, the avuncular gay lecher in "Withnail and I." The low-budget comedy gave him a following so ardent that fans greeted him by quoting his character's most memorable lines. One of the most-quoted: "As a youth I used to weep in butchers' shops."

He made his debut as Harry Potter's ill-tempered Uncle Vernon in 2001's "Harry Potter and the Sorcerer's Stone," the first in the seven-film series based on the bestselling J.K. Rowling novels. He subsequently appeared in "Harry Potter and the Chamber of Secrets," "Harry Potter and the Prisoner of Azkaban" and "Harry Potter and the Order of the Phoenix."

In real life, Griffiths could be as crotchety as Uncle Vernon. He was notorious for halting performances to shame a theater-goer with a ringing cellphone. He did not hide his irritation when strangers approached with unreasonable requests, such as the time the excited father of a Harry Potter fan asked him to say hello to his son on his cellphone. "Get a grip," Griffiths told him and refused.

"I like playing Vernon Dursley in 'Harry Potter,'" the actor told a British newspaper in 2007, "because that gives me a license to be horrible to kids. I hate the odious business of sucking up to the public."

(Times staff writer David Ng contributed to this report.)

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