I'm currently reading Wolf Hall by Hilary Mantel - reference is made to the Cornish rebellion of 1497 "It was the year the Cornishmen came roaring up the country, rebels bent on burning London and taking the English king and bending him to their Cornish will"
The rebellion is a reminder that even at the end of the 15th century England was by no means a homogenous nation. The majority of Cornishmen still spoke their own language rather than English, and regarded their Celtic land as something separate from England."