He gained the joint crown about 847 at a time when the Pictish kingdom had been severely weakened by attacks from the Vikings and were in no condition to dispute his claim. It is said that he invited all the other potential claimants of the throne to a conference to discuss the Viking threat and then had them all killed at a banquet.
He died at Forteviot? in 858 and was buried on Iona. His brother Donald I succeeded him.