Bred by John O'Connor, Ireland. Owned by Thomas Cummins, Ireland. The dam of Flagmount Diamond is the mare Gowan Betty by the Irish Draught stallion New Chieftain. New Chieftain is a son of the stallion Errigal. As King of Diamonds is also a son of Errigal, Flagmount Diamond and his brothers are inbred to Errigal. As well, they are line bred to a great Irish Draught foundation sire, Galty Boy.