From Anglesey, de Tany sent a strong force over the Menai Strait where they were defeated at the Battle of Moel-y-don.

His aggressive policies in Gascony led to many complaints, including a quarrel with Gaston of Béarn and the city of Bazas, where two of Tany's militiamen were killed in February 1274.

During Edward's second campaign against Wales, Tany was appointed on 18 August 1282 commander of the English troops at Anglesey.

He planned to lead an English army via a boat bridge over the Menai Strait to Gwynedd, in an attempt to form a second front at the back of the Welsh.

On 6 November, Tany and his army crossed over the boat bridge, however they were attacked by the Welsh on the opposite side.