This is the second in the Bernicia Chronicles by Matthew Harffy, set in 7th Century Britain. A pretty good setting for a historical fiction writer, as we know very little about it! This pre-dates the Vikings, but is after the Arthurian period.
The story is set in Northumbria and our hero Beobrand is part of King Oswald's forces seeking to destroy the Waelisc (native Britons) invaders led by King Cadwallon. Unusually for this genre, the story starts with major battle. Our hero, a simple warrior, somewhat implausably suggests a night attack to the King and ends up capturing Cadwallon, who is then executed by Oswald. In return for his service he is given his own lands and collects a war band. He has a few problems with his Pict neighbours and has various other adventures and tragedies, but I won't spoil the story.
Historically, there was a battle at Heavenfield, which was important in leading to the domination of England by the Anglo-Saxons. Christianity was beginning to take root amongst the Anglo-Saxons and the establishment of Lindisfarne is also part of the story.
I found the first book in the series a little slow to start with, but it warmed up, and this book is full throttle. Everything you expect from historical fiction in the Cornwell tradition. I have just started the third book, so further reviews shortly.
I am planning to adapt my Age of Arthur figures for some Lion Rampant small scale actions of the period. Here are some Welsh spearmen taking on early Saxons.