at the end of October, where the campaign was celebrated with a tournament. From 29 March to 3 April 1340 Grosmont attended Parliament in London, where a substantial subsidy was voted to the crown. Meanwhile, encouraged by Edward III, the Flemings, vassals of Philip VI, revolted during the winter. They joined forces with Edward's continental allies and launched an April offensive, which failed. A French offensive against these forces commenced on 18 May, meeting with mixed fortunes; Edward's outnumbered allies were desperate for the English army to reinforce them. Grosmont was present at the great English victory in the naval Battle of Sluys in June 1340. The outnumbered English fleet attacked the French and captured or sank 190 of their 213 ships. French losses were between 16,000 and 20,000 killed. The joint French commanders were both captured and one was hanged from the mast of his own ship, while the other was beheaded. Soon after Grosmont was required to commit himself as a hostage in the Low Countries to merchants who had covered the debtsamounting to £9,450the King had incurred. Since Grosmont had personally bound himself to a number of Edward's creditors, he was imprisoned as a debtor. He remained hostage until the next year and had to pay a large ransom for his release. He was only able to join the English army when it laid siege to Tournai as a result of promising that if he did not pay in full he would return voluntarily for a period of further imprisonment. In September Grosmont was part of the embassy which signed the Truce of Espléchin, a five-year suspension of the fighting. Edward was unable to raise the necessary funds to repay his loans and on 25 September Grosmont returned to Malines to, as the King wrote in October, "lay in prison" again. Grosmont was not treated poorly, although the King probably exaggerated his situation for domestic consumption. Grosmont was allowed out on parole to attend jousts several times and received five marks a day expenses. He eventually raised three loans between May and August 1341 to release his bond. Numerous other costs and charges were still due, negotiations over which dragged on until the next year when the King took over the debts. On his return, he was made the king's lieutenant in the north, or Scotland, and stayed at Roxburgh until 1342 when a six-month truce allowed