Dan Brown's page-turning beach read of religious riddles, dodgy Catholic sects and the theory that Jesus had kids should have been an awesome cinematic experience of celestial splendour.

But - lawks a-mercy - director Ron Howard's over-respectfully sombre adaptation is like sitting through a chilly Sunday evensong in a Lancashire methodist church.

His grim reluctance to strip out minor details puts a brake on the action, the narrative is crippled by lack of momentum and tension is never stretched as we're faced with yet another ecclesiastical conundrum.

If you are one of the select few that hasn't read the book then you may well struggle. Basically, Harvard professor Robert Langdon (Hanks sporting what has to be a comedy mullet) is called in to help in a murder investigation.

A highly-respected curator of the Louvre in Paris has joined the choir eternal and it shakes down that he had knowledge of a clandestine sect whose world-shattering secret can be only be revealed by clues cunningly placed in the paintings of Leonardo Da Vinci.

Hooking up with cryptologist Sophie Neveu (Tautou), Hanks sets off to solve the puzzles that will lead him to the mysterious Priory of Sion, the covert organisation that protects the secret of the Holy Grail.

Determined to stop him are whole roster of rotters, including police captain Bezu Fache (Reno, largely wasted), who for no discernible reason believes Langdon to be the killer.

However, Tom's greatest adversary is the menacing albino monk Silas (Bettany), a self-flagellating loon who takes his holy orders from the sinister Bishop Aringarosa (Molina), a member of the right-wing Opus Dei branch of the Catholic Church.

Now the reactionary Opus Dei group do exist...but they're mainly known for religious objections to masturbation rather than a gleeful readiness to contract out killer monks.

Anyway, over the course of one night Robert and Sophie - more father and daughter than potential lovers - hotfoot it from Paris to London with Silas, Bezu and all manner of Papist no-marks on their trail.

Conspiracy theorists who have tired of concocting shady plots around the World Trade Center attack may enjoy themselves as Hanks and Tautou furrow their brows over hidden pointers and wrestle with a medieval Rubik's cube.

But for non-converts the unintentional laughs begin to flow thick and fast, particularly when Ian McKellen hobbles on from panto to play Sir Leigh Teabing, a paranoid aristo who gravely informs us that Jesus and Mary Magdalene tied the knot.

At best slow and at worst turgid, the myriad twists and turns excruciatingly take their toll and, by the time the two hours plus running time is grinding to a halt, many cinemagoers will have lost the will to live...let alone be bothered by yet another pseudo-erudite solution to yet another religious poser.

Praise be when the final credits roll and there endeth the lesson. Amen.

Tim Evans