This is basically a sports film set in the late Middle Ages and definitely not meant to be taken too seriously. The film gets this across early on by having the spectators at a joust sing “We Will, We Will Rock You” and do the wave, and if you looks carefully, you can see a wooden version of the London Eye Ferris wheel in the distance at one point in a later scene.
Heath Ledger plays the squire of a knight who dies partway through a joust when he was close to winning, so Ledger puts on the armor and competes in his stead. He doesn’t do that well, but combined with the real knight’s points it’s enough for him to win the tournament and, more significantly, a prize that will feed him and the other two starving members of the dead knight’s supporting staff, who are played by Mark Addy (star of the sitcom Still Standing and more recently King Robert Baratheon in HBO's Game of Thrones) and Alan Tudyk (the spaceship pilot on Firefly and coincidentally a supporting actor in a lot of films I’ve seen recently). In a stroke of luck they meet someone, namely the young poet Geoffrey Chaucer, who can produce fake patents of nobility that will allow Ledger to keep competing.
The weakest element in the film is Ledger’s love for a young noblewoman played by Shannyn Sossamon. Her character is beautiful but rather a jerk and less appealing than either her maid, played by Bérénice Bejo (the female lead in The Artist and in OSS 117: Cairo, Nest of Spies) or the female blacksmith who joins the crew. At least Sossaman eventually starts acting like a human being, or a mammal anyway.
The whole thing is quite silly, corny, and formulaic. The villainous villain gets his comeuppance, deuses leap out of the machinas just in the nick of time, and there’s even one obvious sports movie cliché you’d think even the makers of this film wouldn’t stoop to, but they do.
Despite all that, I rather enjoyed the show, possibly because it’s so cheerfully blatant in its embrace of well-used story conventions, and maybe I was just in a good mood when I watched it. But a lot of other people liked it as well, so at least I’m not alone. I still would have preferred a heroine a bit less in love with herself, though.