The Duke of Lancaster's party was now in complete possession of all power in the kingdom. It remained to be seen how far they would be able to win the confidence of the people. In the conduct of the war they had been by no means successful. The Duke himself had not mended matters by marrying Constance, daughter of Pedro the Cruel, and assuming in her right the title of King of Castile. This only threw Henry of Trastamare more than ever on the side of France. In 1372 the Earl of Pembroke was sent with an English fleet to assist the Duke of Lancaster. But now the folly of having turned Spain into a bitter enemy became apparent. The English fleet was intercepted by a Spanish fleet, and completely defeated. Pembroke himself was taken prisoner, and the English naval power received a blow from which it took long to recover. Disaster followed disaster in Aquitaine. Rochelle was seized by the French. Thouars, one of the last places of importance remaining to the English, was besieged and hard pressed. When news of all these misfortunes reached Edward III. he was roused from his lethargy, and determined to make one last effort to recover what he had lost. A fleet was equipped, in which Edward himself, and even the Black Prince, whose health was now somewhat better, embarked. But the fleet never reached France. It was beaten about by contrary winds for some weeks, and at last was obliged to return to England. There was now nothing to be done except to ask for a truce. In 1374 the Duke of Lancaster returned to England, leaving all the English possessions, except Bordeaux and Bayonne, in the hands of the French. It was determined that a general congress should be held at Bruges to discuss terms of peace with France. To this congress the Pope and Edward III. were also to send commissioners, to discuss the points at issue between England and the Papacy. John of Gaunt was chief amongst the English Ambassadors, who went to Bruges to try and arrange a peace. John Wiclif went as one of the ecclesiastical commissioners, of whom the Bishop of Bangor was head. There were great difficulties in the way of any peace between England and France. The French wished Edward to give up Calais, but the English would not hear of this. It was only the earnest endeavours of the Pope, Gregory XI., a sincere lover of peace, which finally brought about a truce, to last till June, 1376.