At the same time, the English changed their strategy. Rather than focusing on punitive expeditions as favoured by his father, the young Prince Henry adopted a strategy of economic blockade. Using the castles that remained in English control, he gradually began to retake Wales while cutting off trade and the supply of weapons. By 1407 this strategy was beginning to bear fruit, even though by this time Owain's rebel soldiers had achieved victories over the King's men as far as Birmingham, where the English were in retreat. In the autumn, Owain's Aberystwyth Castle surrendered while he was away fighting. In 1409, it was the turn of Harlech Castle. Edmund Mortimer died in the final battle, and Owain's wife Margaret along with two of his daughters (including Catrin) and three of Mortimer's granddaughters were imprisoned in the Tower of London. They were all to die in the Tower before 1415.