Directed by Lasse Hallstrom. Starring Channing Tatum, Amanda Seyfried, Henry Thomas, Richard Jenkins, Keith Robinson 12A cert, gen release, 105 min

IF THIS insipid blubfest secures just one place in the history books, it will be as the film that finally deposed Avatarfrom the top spot at the US box-office. That's some achievement for a jaundiced three- stone weakling with a limp and a withered arm. There hasn't been such an unlikely turnaround since Mary Kate Olsen shattered James Gandolfini's fibula in three places. (Unless I'm remembering that wrongly.)

Now, it's not as if big stuff doesn't (eventually) happen in Dear John. The boxy, charismatic Channing Tatum appears as a US Marine who, while on leave from Germany, falls in love with the Animé marmoset that goes by the name of Amanda Seyfried. All signs point to a premature happy ending: the couple are well-suited; Tatum's autistic dad warms to his new daughter; the very skies of South Carolina soften accommodatingly.

Then planes crash into the World Trade Center and patriotic Officer Boxy signs back on for the next few pointless wars. Some months later, John (that's actually his name) receives an inexplicable Dear Johnletter from his huge- eyed squeeze. Then somebody gets shot. Then somebody gets sick. Then somebody else gets sick.

Sounds hectic, doesn’t it? The problems are twofold. Firstly (apologies for those semi-spoilers) all this action takes place in the last 45 minutes. To that point, this largely epistolary film progresses like an extended version of the famous 1980 “Sally O’Brien” Harp advertisement.

Secondly, the characters are so heart-stoppingly pallid, worthy, humourless and uninvolved that their very presence would render the storming of the Bastille or the triggering of a supernova hopelessly mundane.

Yet there's a market for these things. Dear John is based on one the many staggeringly successful hanky-dampeners written by Nicholas Sparks. Despite never really securing proper fame, Sparky – check out his The Last Songin two weeks – is one of the phenomena of the age.

Pray he never gets together with James Cameron.