ACTOR Robbie Coltrane has his eight-year-old son to thank for the fact he's starring in what could be one of the biggest movies of all time.

Young Spencer Coltrane gave his famous dad an ultimatum - accept the part of Hagrid in Harry Potter And The Philosopher's Stone or be disowned.

And, according to Robbie, his boy's decision was flawless.

Following the film's worldwide premiere, larger-than-life Robbie beamed: "The fans won't be disappointed".

As one of the most eagerly anticipated films for years, expectations for the big-screen adaptation of JK Rowling's best-selling books have been high.

So many young fans know the books inside out that the pressure on Warner Brothers to get the film right was immense.

But they've succeeded in producing a faithful recreation of Rowling's first book, packed with stunning special effects and founded on sparkling performances from all the main characters.

The cast list is stunning with John Cleese, Robbie Coltrane, Rupert Grint, Richard Griffiths, Richard Harris, Ian Hart, John Hurt, Alan Rickman, Fiona Shaw, Maggie Smith, Julie Walters, Emma Watson, Zoe Wanamaker joining Coltrane in making the film memorable.

But at its heart is Daniel Radcliffe, who plays Harry with the exact blend of modesty and bravery to make him a believable hero.

For anyone who has immersed themselves in the novel world of Harry Potter, this film will be a joy to watch.

For anyone who is yet to read them it will be a perfect introduction to the world of Hogwarts School, of Gryffindor and Slytherin, of high-octane games of Quidditch, and of the power-crazed Professor Snape, a character made delightfully sinister by Alan Rickman's performance.