 Sigtrygg 's fortunes improved in the 1030s . In 1030 , he allied with the King of England , Cnut , and together their fleets raided Wales . A Dublin colony was established in Gwynedd , and for the following years Sigtrygg was at the height of his power . In 1032 , without allies , Sigtrygg won a victory on the Boyne estuary of a type previously unseen by his dynasty for two decades , against a coalition of three kingdoms : over 300 members of the Conailli , the Ui Tortain , and the Ui Meith were captured or killed at the Battle of Inbher Boinne . In 1035 , he plundered the celebrated stone church Ardbraccan in Meath , burned 200 men inside , and carried another 200 off into captivity . ( In revenge , the church at Swords was plundered and burned by Conchobhar Ua Maeleachlainn , who took away cattle and captives . ) 
