What was the last armed conflict between nations to be fought on the soil of the British Isles?

Question

What battle, described as the last great medieval battle in the British Isles, was fought on 9 September 1513 between an invading Scots army under King James IV and an English army commanded by Thomas Howard, Earl of Surrey, and is said to be the largest battle (in terms of numbers) fought between the two nations?

Answer 1

The Battle of Fishguard, 1797
The Battle of Fishguard was fought between French forces in support of the Society of United Irishmen, and British military and civilian forces; it was fought in and around Fishguard, Wales, and eventually ended at sea. There have been many armed conflicts on land in the British Isles, both before and afterwards, but this was the last with an invading force from another country.