Goofs

The barn and horse stalls at Pentragon Hall are obviously built of modern dimensional lumber.

The arrows in Wenneveria's quiver are unusable, as they have no nocks (the slit into which the bow string fits).

Large stone fortifications were not built in Britain until after the Norman invasion at the end the 11th century (almost seven hundred years after the setting of the movie). Fortifications like those shown were not built for an addition two to three hundred years.

Pendragon Hall contains a large stone fireplace and chimney. The earliest chimneys in the British Isles were not built until at least the end of the 12th century, a bit late for the 5th century setting of the movie.

All of the men appear either clean shaven or with neatly trimmed facial hair. In the fifth century even the best groomed individuals would only shave (or be shaven) about once per week; and then it would be anything but "clean".

Much of the arms and armor shown is consistent with the later Dark and Middle Ages rather than the end of the Roman period in Britain.