Despite the crushing defeat at Sluys, within ten days of the battle English spies reported fresh French naval activity in the Channel ports. The western fleet had been disbanded, the council believing the French threat had sunk with the Grand Armee de la Mer. The brief absence of French shipping did allow Sir Thomas Ferrers to land on Guernsey with a small Southampton fleet on 13 July 1340. He returned most of the island to English control, laying siege to Castle Cornet four days later. The remnants of the French fleet consisted of three galleys and seven barges. These were hurriedly reinforced by a squadron of Castilian galleys and put to sea under the command of the new French admiral John Houdetot. This force captured some English merchants ferrying supplies to Scotland before the end of July. On 26 July, Houdetot then attacked a wool convoy heading for Flanders, taking thirty ships. The wool was further pay for Edward’s allies. Its loss was tantamount to a direct raid on his treasury.

Four days later Houdetot struck again, landing a raiding party on the Isle of Wight which inflicted heavy casualties on the local militia. The militia commander was killed and considerable damage caused before the raiders were driven off. The next day the French raided Portland and burned Teignmouth, before unsuccessfully attempting to break in to Plymouth. The French headed back to their ports on 5 August. Although the attacks were unexpected, Edward’s council was now used to French raiders. The western fleet was hurriedly concentrated in the Downs near Winchelsea in its accustomed defensive role under Clinton’s command. Meanwhile Morley went on the offensive, heading to the Channel Islands to support Ferrers. The coastal militias were mustered, and convoys reimposed. When Houdetot’s fleet put to sea on 29 August, he was unable to make an impression. Equally unable to find the raiders, Morley’s fleet loitered near the mouth of the Seine taking shipping before suddenly descending on Brest. The English invaded the port, and captured merchant shipping, including six ships from Genoa worth more than >10,000. The attack punished Duke John III of Brittany for his staunch allegiance to the French.

Edward’s success at Sluys had persuaded parliament to provide him with immediate funds, allowing his coalition army to take the field.