 In 1345 Edward III was planning a major assault on France . A three @-@ <unk> attack would have the Earl of Northampton attacking from Brittany , the king himself from Flanders , while Grosmont was dispatched to <unk> to prepare a campaign in the south . Moving rapidly through the country , he confronted the Comte d ’ Isle at <unk> on 21 October and there achieved a victory described as " the greatest single achievement of Lancaster 's entire military career " . The ransom from the prisoners has been estimated at £ 50 @,@ 000 . The next year , while Edward was carrying out his <unk> campaign , Grosmont laid siege to , and captured , <unk> , before returning home to England in <unk> . 
