The Battle of Brunanburh took place in 937, and is often referred to as the battle that made England. But there are a LOT of questions about that battle, including how it played out and where it took place.
Research:

SYMHC Classics: Gustave Courbet
40:51

Behind the Scenes Minis: Oh, Kropotkin!
17:28

Peter Kropotkin's Mutual Aid, Part 2
49:57