David Hemmings stars as the king. And Michael York is the Danish "villain" Guthrum. Ian McKellen has a role too :-) It is a British film, so Hollywood didn't have much to do with it. As I recall it was pretty cool, but also had some rather "dead" periods where it dragged.

The testudo, once it deploys, doesn't move, but forms a rock-like bastion upon which the Danes hurl themselves in ferocity. It would have failed Alfred in the end, except he sent to the local peasants for help and they came in a gaggle (including some rather wild looking women) upon the rear of the Danish horde and broke its concentration, so that Alfred and his boys could counterattack.

I only saw a chopped version years ago on TV. I would like to see the whole thing someday.