RICHARD GRIFFITHS, one of Britain's most celebrated character actors, has died from complications following heart surgery.
The stage and screen star, who played Uncle Vernon Dursley in the Harry Potter films, was 65.
Daniel Radcliffe, who played Harry Potter alongside him, led tributes to the actor whose "encouragement, tutelage and humour" made work "a joy".
Radcliffe, who also performed with Griffiths in the stage play Equus, said: "Richard was by my side during two of the most important moments of my career.
"In August 2000, before official production had even begun on Potter, we filmed a shot outside the Dursleys', 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, terrified as I was, his encouragement, tutelage and humour made it a joy.
"In fact, any room he walked into was made twice as funny and twice as clever just by his presence. I am proud to say I knew him."
Griffiths died yesterday at the University Hospital of Coventry and Warwickshire.
Sir Nicholas Hytner, director of the National Theatre, said Griffiths's unexpected death would devastate his "army of friends".
He said: "Richard Griffiths wasn't only one of the most loved and recognisable British actors - he was also one of the very greatest.
"His performance in The History Boys was quite overwhelming: a masterpiece of wit, delicacy, mischief and desolation, often simultaneously.
"But that was just one small part of a career that spanned Shakespeare, cutting-edge new plays and major work in film and television."
Sir Nicholas, who directed Griffiths in The History Boys and The Habit Of Art, added: "His currency as an actor was truth; as a colleague it was hilarity.
"His anecdotes were legendary. They were, literally, endless. They would go on for hours, apparently without destination, constantly side-splitting.
"The only way to stop them was to tell him you were walking away, though there were always others in the audience so, as far as I know, he never stopped. He was the life of every party."
Away from the Harry Potter films, Griffiths was most famous for his role as Uncle Monty in cult favourite Withnail And I.
The married actor, who was born in Thornaby-on-Tees, North Yorkshire, and grew up caring for his deaf parents, was awarded an OBE for services to drama in 2007.
His agent Simon Beresford said: "Richard brightened my days and enriched the life of anyone he came into contact with.
"On stage he allowed us to share in our own humanity and constantly question our differences.
"Richard gave acting a good name. He was a remarkable man and one of our greatest and best-loved actors. He will be greatly missed.
"Our thoughts and deepest sympathy go to his devoted wife Heather and his family at this sad time."
Thea Sharrock, who directed Griffiths in Equus, Heroes and Sunshine Boys, said: "I worked with Richard more times than any other actor.
"Everybody knew he was my favourite. He was the most tender, gentle, kind, generous, loving man.
"His curiosity was unending, as was his striving for perfection. I cannot imagine a world without all those stories. I will miss him so very very much."
The producers of Heroes and Equus, David Pugh and Dafydd Rogers, described the actor as a "great man, a great character, a great talent greatly missed".
In a joint statement they said: "He was a glorious man and we were so honoured to have known him."
Griffiths, born on July 31 1947, left school at 15 but later returned to education to study drama, before joining the Royal Shakespeare Company.
He married Heather Gibson in 1980 after they met during a production of Lady Windermere's Fan in 1973.
His early television career saw him land bit parts in series such as Minder, The Sweeney and Bergerac.
Film credits included Chariots Of Fire, The French Lieutenant's Woman, GoldenEye, Gandhi and The Naked Gun 2 1/2.
Withnail & I, which starred Richard E Grant and Paul McGann as two out-of-work actors and Griffiths as the predatory Uncle Monty, was released in 1987. Shot on a shoestring budget and with little plot to speak of, it was largely ignored when first released but is now regarded as a British classic.
Griffiths went on to star as a crime-solving chef in TV series Pie In The Sky during the 1990s, and made his first appearance as Uncle Vernon in Harry Potter and the Philosopher's Stone, released in 2001.
He has earned endless plaudits for his stage and screen career, including a Laurence Olivier Award for his performance as inspirational teacher Hector in Alan Bennett's The History Boys.
The same role also earned him a Tony Award when the production transferred to Broadway.
The portly actor was known for his zero-tolerance approach to mobile phones in theatres.
In 2004 he ordered a man out of the National Theatre when his phone repeatedly rang during a performance of The History Boys. The following year he stopped mid-speech during a production of Heroes at Wyndham's Theatre to scold a woman whose phone kept going off.
The actor, who starred alongside Danny DeVito in Neil Simon's The Sunshine Boys at the Savoy Theatre, last year, was due to reprise the role in September in Los Angeles.
Richard E Grant paid tribute to his late co-star on Twitter.
He wrote: "My beloved 'Uncle Monty' Richard Griffiths died last night. Chin-Chin my dear friend."
Quoting one of the actor's comic lines from Withnail And I, broadcaster Danny Baker wrote: "Richard Griffiths has died: 'The carrot has mystery. Flowers are essentially tarts. Prostitutes for the bees.' RIP old cork."
Further tributes from fans flooded the social networking site where "#RIPRichardGriffiths", "Withnail" and "Uncle Vernon" became trending topics this morning.