According to the studio advertising campaign, the 2004 mega-budget version of "King Arthur" is "the untold true story that inspired the legend" -- you know, the factual version in which Arthur is a brooding bore, Lancelot has hip, runway-model facial hair and Guinevere is a half-naked post-feminist warrior hottie.

Borrowing superficially from recent theories about Camelot's origins only as a jumping off point -- producer Jerry "Armageddon" Bruckheimer cares about cool explosions and box office receipts, not historical accuracy -- this commercialized concoction draws its regal hero (played by rising star Clive Owen) as an idealistic, half-Anglo high commander in the Roman army, which is in the midst of abandoning Britannia as a protectorate.

Arthur and his knights (Sarmatian soldiers reluctantly bound to imperial service) take it upon themselves to defend the now unguarded territory against invading hoards of barbarian Saxons from the north. But first they're sent on one last suicidal mission into Saxon territory to rescue a rich Roman family living there for no explored reason.

Along the way they loose their respect for Rome, they save Guinevere (yummy Keira Knightley of "Pirates of the Caribbean" fame) from the uppity Latin landowner's dungeon -- and thereby ally themselves with her forest-dwelling clan of warriors led by a non-magic Merlin (Stephen Dillane) -- and they have a few run-ins with the Saxons that provide the film's only sparks of life.

Having abandoned all the utopianism and human interest inherent in the King Arthur legend (this origin story includes barely a flicker of romance between Arthur and Guinevere, save one abrupt sex scene, and no love triangle with Lancelot at all), writer David Franzoni and director Antoine Fuqua rely on their battle scenes to keep the audience awake.

Creative combat strategies do the trick for a few minutes at a time (Arthur's handful of knights trick a large Saxon battalion into marching out onto the too-thin ice of a frozen lake), but most of these scenes are so badly shot and edited that they become just a visual frenzy of PG-rated blood, mud and swords going thud. Without a single perspective shot, at first it's even hard to tell if the picture's climax takes place at a castle or along Hadrian's Wall, the 72-mile fortification marking the northern border of Roman England.

This scene also got a huge laugh from a preview audience last week when Guinevere made her dramatic entrance in ridiculous boob-baring battle garb (who designed these costumes? Jean-Paul Gaultier?), ready to kick some broadsword butt. Nevermind that a 105-lb. girl with arms the width of carrot sticks couldn't even lift a 5th century broadsword.

Franzoni ("Gladiator") attempts to justify his modern-grrrl take on Guinevere by portraying her as a Pict -- a culture that may have had female warriors and may have gone into battle naked and painted blue to intimidate the enemy (although probably not in the dead of an English winter). But the movie doesn't explain any of this -- her ethnicity is just an excuse to show some skin.

He and Fuqua ("Training Day") don't bother much with character development either. Knightley had far more depth to work with as an equally contemporary take-charge damsel in tongue-in-cheek "Pirates" (which didn't need to explain her 21st-century demeanor because it never claimed to be realistic). Lancelot (Ioan Gruffudd of A&E's "Horatio Hornblower") is good-looking but otherwise completely interchangeable with the rest of the scruffier, bellicose Round Table knights. And while the dramatically potent Owen ("The Bourne Identity," "Croupier") sinks his teeth into the title role, this Arthur doesn't give him anything to chew on -- he's an off-the-shelf Conflicted Action Hero With Emotional Baggage.

"King Arthur" does offer up hints of realism here and there (young Arthur pulls the sword Excalibur not from a stone but from his father's burial mound when his village is attacked), but it is first and foremost an action movie aimed at the teenage boys that are the bread and butter of summer-blockbuster moviemaking -- and a tedious one at that.