Gwilym ap Tudur Rhys and Owain Glyndŵr. As a result, the Tudur brothers began planning an attack on Conway Castle. On Good Friday, 1 April 1401, the brothers and 44 men (which included those who had also been excluded from the pardons) infiltrated the castle. They had pretended to be carpenters, and captured the castle while the guard were in church. Negotiations began for the return of the castle on 13 April, with the king represented by Henry "Hotspur" Percy and Gwilym representing the Welsh forces. After seeking a compromise, which would have resulted in pardons being given to the Welshmen, the king
Owain Glyndŵr the French. The result was a formal treaty that promised French aid to Owain and the Welsh. The immediate effect seems to have been that joint Welsh and Franco-Breton forces attacked and laid siege to Kidwelly Castle. The Welsh could also count on semi-official fraternal aid from their fellow Celts in the then independent Brittany and Scotland. Scots and French privateers were operating around Wales throughout Owain's war. Scottish ships had raided English settlements on the Llŷn Peninsula in 1400 and 1401. In 1403, a Breton squadron defeated the English in the Channel and devastated Jersey, Guernsey and Plymouth, while