You should know the story. The curator of the Louvre is found dead, spread-eagled on the museum's floor, having carved symbols into his own naked flesh, prompting a red herring filled chase across Paris, London and Edinburgh as, on the run from French special agent Bezu Fache (Jean Reno) who believes him the killer, religious symbologist Robert Langdon (Tom Hanks) and cryptologist French cop Sophie Neveu (Audrey Tautou) seek to solve the Leonardo Da Vinci linked riddles that will reveal the secret hiding place of the Holy Grail.
Dan Brown's book has sold millions around the world, igniting controversy over the plot's claims that the Church has maintained a two century long cover up regarding the true nature of the Grail and that Christ and Mary Magdalene got hitched and had kids.
Against his better judgement, director Ron Howard was persuaded not to hold any test screenings of the film because the studio wanted to preserve the mystery (sic) of the plot.
Consequently, the first time non-insiders saw it was on Tuesday night. Had preview audiences had their chance to fill in those reaction cards, then they might have told Ron that his adaptation was, for the most part, narratively faithful to the book but, unlike its clumsily written but page-turning counterpart, lacking in energy, suspense and excitement.
They may have also said it was overlong, and that the ending (where, after over two hours of trying to decipher the clues, everything is quite literally laid out on the table, neatly filed and indexed and pretty much available to anyone with the admission price to Edinburgh's Rosslyn Chapel.)
Some might have been put off by the fact that a good proportion of the film is subtitled, but rather more of a problem is the fact that when the French cast speak in English, the accents often render the dialogue hard to follow.
Other comments might have included the note that Hanks, sporting perhaps the most irritating hairstyle of his career, is unusually stiff, flat and uninvolving. But then, having to deliver the unintentionally hysterical line "I have to get to a library, fast" with a straight face is enough to drain the enthusiasm from anyone.
Still, he's not alone in the lacklustre acting ranks. Tautou (who has absolutely no chemistry with Hanks) could be reading from cue cards for all the expression and emotion she brings to the role while, as the conniving Bishop Aringarosa from the ultra conservative Opus Dei council that is dedicated to destroying the Grail secret and its guardians, the Priory of Sion, Alfred Molina borders on the cartoon.
And, sad though it is to say, Reno, once one of France's most exciting stars, now seems to have lost all interest in acting, content to just walk through the motions. Still, at least he looks more comfortable than he did in The Pink Panther.
Thank heavens then for Paul Bettany, chewing scenery with gusto and a dodgy Italian accent as the killer fanatic albino monk Silas who's hot on Langdon and Neveu's trail, stopping only to indulge in what the BBFC have amusingly termed "mild flagellation" (I suppose it depends on what the examiner's used to) to expunge his sins.
And, let us not forget the marvellous Ian McKellen who, as crippled Grail obsessive Sir Leigh Teabing, injects the film with what little fire and, thankfully, humour it possesses, rolling the lines around his tongue with relish while his eyes twinkle with the fun.
A shame you have to wait almost 90 minutes.
Those not accustomed to have to work at their popcorn blockbusters would doubtless have complained about the film's heavily talky nature as reams of arcane historical lore are expounded.
But, as the scene where Teabing expounds the true hidden meaning of Da Vinci's The Last Supper shows, it would have a lot better had Howard trusted his audience to listen and digest rather than intercutting biblical and medieval tableau flashbacks of crusaders, Romans and even Mary giving birth that look like a mix of ungraded outtakes from Kingdom of Heaven and a bad educational CD-Rom.
Howard might have taken comfort from praise for the film's lustrously dark look, use of locations and production design. But, while it's not actually dull, one suspects the consensus of opinion would have described the performances unengaging, the score over-blown, and the film too often melodramatic, repetitive, and lifeless.
Humiliatingly, some may have remarked that it's not a patch on that Da Vinci Code knock off, National Treasure. And perhaps at least one might have wondered why the dead, naked old curator had a dazzling white light obscuring his groin like some perverse halo.
Maybe that's why the didn't let Ron do his test screenings after all. I think the Catholic Church can still sleep easy.
Our verdict: 3 stars out of 5