From their own site:
"Brytenwalda is a ruleset which will allow you to recreate battles and raids during the so called British “Age of Arthur” and Saxon invasion. In Brytenwalda you'll impersonate a Chieftain during the Dark Ages, commanding his men in the defence of their homelands or looting and burning those belonging to your enemies.This looks awesome, with great production values for a free set. I am very keen to give it a try, even if I have to use Vikings to do so for now. It is an excellent excuse to get some Romano British figs eh? I bet Jason could be persuaded that he needs Saxons to provide generic 'Men of Middle Earth' for his Rohan and Isengard forces too.
Although the Dark Ages were an extremely violent era with a great number of battles and raids, but only a few were detailed in the chronicles, such as decisive pitch battles or those in which an important person died. Brytenwalda is focused on these kinds of battles which the modern wargamer would call a “skirmish”. While you wont be able to re-enact the Battle of Hastings in Brytenwalda, you'll have plenty of fun leading a band of Scot-Irish pirates, a group of raiding Saxons or a unit of Romano-British pedites patrolling the frontier.
It is for mature gamers because it is not focused in competitive manners nor thought as game for tournaments. This is just for fun... and fun is what a game should be." (http://brytenwalda.blogspot.com/)
See, this is why I used the movement trays for my historicals!