His reign began in the year 900 when he succeeded his cousin Donald II of Scotland and would continue to reign for 43 more years. In 904 he defeated Vikings at the Battle of Streathearn. He oversaw the founding of England by king Æthelstan in 927. He is defeated by Æthelstan in 937 who proclaims himself king of Britain. People in Scotland, Wales, England and Ireland began to cal Æthelstan our father and our lord, and our king. He died in 939 and by 943 Edmund I of England began to invade Scotland to rule the whole of Britain. Constantine, scared of being killed abdicated. Proclaiming he could not handle the English forces. 