William I

Known as “William the Lion”, this Scottish king notched up 48 years and 360 days on the throne from 1165 to 1214 (not to be confused with William I of England, whose reign started a hundred years earlier). He was posthumously given the nickname “Lion” because his standard was a red lion – the same one that is now incorporated into the Royal Standard of the United Kingdom. As well as being King of Scotland, he was also Earl of Northumberland, but had to give up that title to Henry II of England, which would cause William to spend much of his reign fighting to get it back. He joined the Great Revolt against Henry and later clashed with Henry’s son John as well. Another Scottish monarch that spent his reign fighting the English.