St Columba is one of the most important figures in the early history of the British Isles. A native of Donegal and a nobleman of royal ancestry, his outstanding religious career spanned both sides of the Irish Sea. On the Scottish island of Iona he founded his principal monastery where he served as abbot until his death in AD 597. Iona eventually became the centre of a powerful federation of monasteries that preserved a memory of Columba and nurtured the saintly cult that grew around him. Drawing on contemporary sources – particularly the writings of Adomnán, abbot of Iona from 679 to 704 – and the latest modern research, this book traces Columba's achievements and legacy. It examines his roles as abbot, scholar and missionary as well as his involvement in the affairs of kings in both Ireland and northern Britain.