By Caroline Briggs
BBC News entertainment reporter
Ron Howard's adaptation of The Da Vinci Code, which debuts at Cannes Film Festival, fails to live up to the hype that surrounded Dan Brown's novel.
When the curator of Paris's Louvre museum is found dead with a trail of symbols and clues written in his blood, Professor Robert Langdon (Tom Hanks) is drafted in to help decipher the mysterious daubings.
But the brilliant Harvard symbologist is warned by police cryptologist Sophie Neveu (Audrey Tautou) - also the dead man's granddaughter - that his own life is at risk.
The pair then embark on a thrilling journey across Paris, London and Scotland in a quest to crack the code, find the Holy Grail, and uncover a massive religious conspiracy.
Set against stunning backdrops including the Louvre, Temple Church and Westminster Abbey, The Da Vinci Code is visually handsome.
And with only a few cinematic additions, fans of Dan Brown's novel will be pleased to see that the film remains largely faithful to the best-selling book.
Sir Ian McKellen brings energy to the film as Leigh Teabing
Director Ron Howard has stuck to the central theme - that Jesus Christ married Mary Magdalene and had children whose descendants still survive today.
Taking its cue from the book, conservative Catholic group Opus Dei is depicted as a murderous and power-crazed organisation.
But Howard, who won an Oscar for A Beautiful Mind, faced a tougher challenge in translating Brown's narrative to the big screen. And his fondness for historic flashbacks and other gimmicks to tell the story border on patronising.
They are too obviously used to help gel together the two-and-a-half hour screenplay whose storyline may prove confusing for those who have not read the book.
One of the book's triumphs is the way in which it allows the reader to solve the clues before Langdon and Neveu, giving the reader a smug satisfaction at their own perceived intelligence.
The film does not allow the same satisfaction, but instead must join protagonists Langdon and Neveu on their convoluted journey.
For those familiar with the book, it poses its own problems.
Bettany puts in a good performance as the murderous monk Silas
While the plot worked its magic on the pages, it does not transfer well to the screen - here, it is long and it is dull.
Scriptwriter Akiva Goldsman has produced a script that is clunky in parts and downright cringeworthy in others.
While all the cast deliver competent performances, Hanks is dry and uninspiring as Langdon - and the mullet hairstyle he sports throughout deserves a credit of its own.
Tautou brings a certain Gallic charm to her role as Neveu, but her stilted performance falls short of the 2001 hit Amelie.
It is left to British thespian Sir Ian McKellen to light up the screen as theological historian Leigh Teabing, and his ability to deliver a line with conviction and inject some hearty humour is welcome.
Paul Bettany is menacing as Silas the albino assassin monk whose self-flagellating and murder scenes are more than a little unnerving.
Together McKellen and Bettany prevent the film from being a £125m critical disaster.
But the truth is, the wide appeal of The Da Vinci Code book coated the film in critic-proof armour long before it was even made.
With 50 million copies of the book sold worldwide, it is virtually guaranteed to be a commercial hit.