At first after his release Stephen carried on the work of restoration rapidly and without interruption. London received him with joy. At Christmas time he wore his crown at Canterbury; he was probably, indeed, re-crowned by the archbishop, to make good any defect which his imprisonment might imply. Already, on December 7, a new council, assembling in Westminster, had reversed the decisions of the council of Winchester, and, supported by a new declaration of the pope in a letter to the legate, had restored the allegiance of the Church to Stephen. At the Christmas assembly Geoffrey de Mandeville secured from the king the reward of his latest shift of sides, in a new charter which increased a power already dangerous and made him an almost independent prince. In the creation of two new earls a short time before, William of Albini as Earl of Sussex or Arundel, and Gilbert of Clare as Earl of Hertford, Stephen sought to confirm a doubtful, and to reward a steady, support. No event of importance marks the opening months of 1142. Lent was spent in a royal progress through eastern England, where as yet the Empress had obtained no footing, to York. On the way, at Stamford, he seems to have recovered the allegiance of the Earl of Chester and of his brother, the Earl of Lincoln, a sure sign of the change which had taken place since the battle in which they had overcome him so disastrously a year before. In the summer Stephen again assumed the offensive and pushed the attack on his enemies with energy and skill. After a series of minor successes he advanced against the Empress herself at Oxford, where she had made her headquarters since the loss of London. Her brother Robert, who was the real head of her party, was now in Normandy, whither he had gone to persuade Geoffrey to lend the support of his personal presence to his wife's cause in England, but he had made sure, as he believed, of his sister's safety before going. The fortifications of Oxford had been strengthened. The barons had pledged themselves to guard Matilda, and hostages had been exacted from some as a check on the fashion of free desertion. It seems to have been felt, however, that Stephen would not venture to attack Oxford, and there had been no special concentration of strength in the city; so that when he suddenly appeared on the south, having advanced down the river from the west, he was easily able to disperse the burghers who attempted to dispute his passage of the river, and to enter one of the gates with them in their flight. The town was sacked, and the king then sat down to a siege of the castle. The siege became a blockade, which lasted from the end of September to near Christmas time, though it was pushed with all the artillery of the age, and a blockade in which the castle was carefully watched day and night. Stephen seems to have changed his mind since the time when he had besieged Matilda in Arundel castle, and to have been now determined to take his rival prisoner.