He is indeed. I included him as a minor player in the first novel I wrote, but soon became intrigued enough to want to write a novel with him as the protagonist. So far all I have is copious quantities of notes and extracts, but I'll get there eventually!Is he the subject of your research, out of interest?
For the Kingdoms of the North trilogy...yes, I came across them a couple of years ago when I first starting researching Rheged (the research has been going somewhat slowly, for various reasons) - I've managed to get hold of all three, although so far I've only read Bride of the Spear. It's a very enjoyable read, and I love the fact that although Kathleen Herbert doesn't pull her punches with regard to certain events, she still gave it a satisfyingly happy ending. I'll have to read the other two soon, but I've just started Sutcliff's Sword at Sunset, so they'll have to be patient! Looking forward to it, though.