cemented, there had been few casualties and the French King had been distracted from the Black Prince's preparations for a greater in south-west France. Loire campaign In August 1356 Grosmont marched south from eastern Brittany in another . It was his intention to join the army of Edward, the Black Prince, the eldest son of Edward III. This had marched north from Bergerac on 8 August. It was planned that the two would meet in the general vicinity of Tours. Grosmont brought with him from Normandy 2,500 men. He also had under his command over 2,000 men garrisoning the English-held fortifications of Brittany. The extent to which he added the men from these garrisons to the troops from Normandy is not known. Due to the unseasonable fullness of the River Loire, across which the French had destroyed or strongly fortified all the bridges, Lancaster was unable to effect a junction. In early September he abandoned the attempt to force a crossing at Les Ponts-de-Cé and returned to Brittany. En route he captured and garrisoned a substantial number of French strongpoints. The Black Prince also returned towards his starting point, but his delay in waiting for Lancaster near Tours enabled a French army under the command of their king to overtake him. As a result the Prince was forced to commit to the Battle of Poitiers, where the French were heavily defeated and King John was captured. 1356–1360 Returning to Brittany from the Loire campaign, Grosmont laid siege to its capital, Rennes. He participated in the last great offensive of the first phase of the Hundred Years' War: the Rheims campaign of 1359–1360. Then he was appointed principal negotiator for the Treaty of Brétigny. This ended the Hundred Year's War with the English achieving very favourable terms. Death and burial After returning to England in November 1360, he fell ill early the next year, and died at Leicester Castle on 23 March 1361. It is possible that the cause of death was the plague, which that year was making a second visitation to England. Mortimer argues against the plague being the cause of death, as Grosmont made his will ten days before his death, a space of time inconsistent with the usual swift progress of the plague and his illness and death in early 1361 is inconsistent with reports of the spread of plague in England beginning in May. He was