Manny also took part in the campaigns of the Earl of Derby in Guyenne, being present at the battles of Bergerac and Auberoche. He was summoned to parliament as a baron by writ from 12 November 1347 to 8 January 1371. In 1359, he was made a Knight of the Garter, succeeding John, Lord Grey (died 1 September 1359), and at various times he received extensive grants of land both in England and in France. He was frequently employed by King Edward in the conduct of diplomatic negotiations as well as in military commands. He was one of those charged with the safe custody of the French king John II when a prisoner at Calais in 1360; in 1369 he was second in command under John of Gaunt in his invasion of France.