Although negotiations with the lords of Ireland were unsuccessful, Owain had reason to hope that the French and Bretons might be more welcoming. He dispatched Gruffydd Young and his brother-in-law (Margaret's brother), John Hanmer, to negotiate with 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 the French made a landing on the Isle of Wight. By 1404, they were raiding the coast of England, with Welsh troops on board, setting fire to Dartmouth and devastating the coast of Devon.