With the outbreak of the Hundred Years ' War in 1337 , Grosmont 's attention was turned towards France . He took part in several diplomatic missions and minor campaigns and was present at the great English victory in the naval Battle of Sluys in 1340 . Later the same year , he was required to commit himself as hostage in the Low Countries for the king 's considerable debts . He remained hostage until the next year and had to pay a large ransom for his own release . On his return he was made the king 's lieutenant in the north and stayed at Roxburgh until 1342 . The next years he spent in diplomatic negotiations in the Low Countries , Castile and Avignon .