The film was bad, but it was nice to see an attempt to show something other than the usual daft Chivalric Arthurian legends.

Lucius Artorius Castus, played by Clive Owen in the movie, was a prefect in Legio VI Victrix which guarded Hadrian's Wall, at a point in his career when his expected rank would be prefect alae, ie. commanding cavalry auxilia. During this posting the Picts invaded and the VI Victrix fragmented and mutined after the Picts killed their legate, allowing the invaders to ravage the lands on the eastern side of the Pennines. However, the prefect in charge of the fort at Bremetennacum (modern Ribchester), where many Sarmation cavalry were based, managed to keep order on the western side. After the invasion was repelled the officers of the VI Victrix were either executed or in effect exiled to remote posts. Unlike what happened to his peers, Castus was promoted to Dux of the cavalry in Britain, making it all too possible that he was the prefect who commanded the fort at Bremetennacum.

So if they wanted to explore the theory that Lucius Artorius Castus is the ultimate origin of the legend of King Arthur, it should have been a Pictish invasion in the movie and not time travelling Saxons. Of course, we can't have that in Hollywood, since the Picts are from Scotland and that makes them Scottish, right? Oh, and the Saxons, well everybody just knows that means Anglo-Saxons, making them the evil English. Yey! It's Braveheart again! *sigh* Damned Hollywood.