 He raised a rebellion and allying himself to the Welsh prince of Gwynedd (and Powys), Bleddyn ap Cynfyn, and his brother Riwallon, he unsuccessfully attacked the Norman castle at Hereford in 1067.They did not take the county, and retreated to Wales to plan further raiding.During the widespread wave of English rebellions in 1069–70, he burned the town of Shrewsbury and unsuccessfully besieged Shrewsbury Castle, again helped by his Welsh allies from Gwynedd, as well as other English rebels from Cheshire.