In 1284 he joined with other Scottish noblemen who acknowledged Margaret of Norway as the heir of King Alexander III.[1] He was a Guardian of the Realm from 1286 to 1292.[2] Comyn submitted to the English king in July 1296 at Montrose.[3]
Comyn, head of the most powerful noble family in Scotland, was a committed ally of Balliol and assisted him in his struggle against Edward I of England. It has even been suggested that the Comyn family was the driving force behind both the Balliol kingship and the revolt against Edward's demands.
John Comyn is credited with the building of several large castles or castle houses in and around Inverness. Parts of Mortlach (Balvenie Castle) and Inverlochy Castle still stand today. John Comyn as his father was before him was entrusted by King Alexander III with the defence of Scotland's northern territories from invasion by the Vikings and the Danes.