Following the death of King Alexander III like most Clans with a Norse connection, Sir John Lamont, Laumon’s grandson and the Chief of the clan, fought for the Balliol faction and sided with the MacDougall’s of Lorne against Robert the Bruce. When Bruce won the Lamonts suffered along with their allies. Once Robert the Bruce was firmly situated on the throne, he and his line took vengeance against the clans that had opposed him. In 1371, Robert II gave the Lamont hereditary seat at Dunoon to Bruce supporter Sir Colin Campbell, Black Knight of Loch Awe.

By the end of the 14th century, almost all of Clan Lamont’s original Cowal territory had been lost to the Campbells. In spite of considerable intermarriage between Clan Campbell and Clan Lamont, the relations between Campbell clansmen and Lamont clansmen remained harsh and bitter