The victory at Lincoln changed the situation of affairs at a blow. From holding a little oval of territory about the mouth of the Severn as the utmost she had gained, with small immediate prospect of enlarging it, Matilda found the way to the throne directly open before her with no obstacle in sight not easily overcome. She set out at once for Winchester. On his side, Bishop Henry was in no mood to stake his position and influence on the cause of his brother. Stephen's attitude towards him and towards the Church had smoothed the way for Matilda at the point where she might expect the first and most serious check. The negotiations were not difficult, but the result shows as clearly as in the case of Stephen the disadvantage of the crown at such a crisis, and the opportunity offered to the vassal, whether baron or bishop, who held a position of independent strength and was determined to use it in his own interests. The arrangement was called at the time a pactus - a treaty. The Empress took oath to the bishop that all the more important business of England, especially the filling of bishoprics and abbacies, should be done according to his desire, and her oath was supported by those of her brother and of the leading barons with her. The bishop in turn received her as "Lady of England," and swore fealty to her as long as she should keep this pact. The next day, March 3, she entered the city, took possession of the small sum of money which had been left in the treasury by Stephen and of the royal crown which was there, entered the cathedral in solemn procession, supported by Henry and the Bishop of St. David's, with four other bishops and several abbots present, and had herself proclaimed at once "lady and queen of England," whatever the double title may mean. Certainly she intended to be and believed herself nothing less than reigning queen.[41] Without waiting for any ceremony of coronation, she appointed a bishop, created earls, and spoke in a formal document of her kingdom and her crown.

Directly after these events Henry of Winchester had summoned a council, to learn, very likely to guide, the decision of the Church as to a change of allegiance. The council met in Winchester on April 7. On that day the legate met separately, in secret session, the different orders of the clergy, and apparently obtained from them the decision which he wished. The next day in a speech to the council, he recited the misgovernment of his brother, who, he declared, had, almost immediately after his accession to power, destroyed the peace of the kingdom; and without any allusion to his deposition, except to the battle of Lincoln as a judgment of God, and with no formal action of the council as a whole, he announced the choice of the Church in favour of Matilda. The day following, a request of the Londoners and of the barons who had joined them for the release of Stephen, and one of his queen's to the same effect, was refused. The Empress was not present at the council. She spent Easter at Oxford, receiving reports, no doubt, of the constant successes her party was now gaining in different parts of England. It was not, however, till the middle of June that London, naturally devoted to Stephen, was ready to receive her.

Her reception in London marks the height of her success. She bought the support of the powerful Geoffrey de Mandeville by confirming to him the price which he had extorted from Stephen, the earldom of Essex, and by bidding higher than her rival with gifts of lands, revenues, and privileges which started him on the road to independence of the crown, which he well knew how to follow. Preparations were no doubt at once begun for her coronation. Her uncle King David came down from Scotland to lend it dignity, but it was destined never to occur. Her fall was as rapid as her rise, and was due, even more clearly than Stephen's, to her own inability to rule. The violent and tyrannical blood of her uncle, William Rufus, showed itself in her as plainly as the irresolute blood of Robert Curthose in her cousin, but she did not wait to gain her uncle's security of position to make violence and tyranny possible. Already, before she came up to London, she had offended her followers by the arrogance and harshness of her conduct. Now these traits of character proved fatal to her cause. She greatly offended the legate, to whom she was as deeply indebted as Stephen had been, and whose power to injure her she might easily understand, by refusing to promise that Eustace might hold his father's continental counties of Boulogne and Mortain. Equally unwise was her attitude towards London. She demanded a large subsidy. The request of the citizens for a confirmation of the laws of King Edward, because her father's were too heavy for them, she sternly refused. Queen Matilda, "acting the part of a man," advanced with her forces to the neighbourhood of the city and brought home to the burghers the evils of civil war. They were easily moved. A sudden uprising of the city forced the Empress to "ignominious" flight, leaving her baggage behind. She retreated to Oxford, and Matilda the queen entered the recovered city. Geoffrey de Mandeville at once brought his allegiance to the new market and obtained, it is probable, another advance of price and Henry of Winchester was easily persuaded to return to his brother's side. "Behold," says the historian of the Empress's party, "while she was thinking that she could immediately possess all England, everything changed." He adds that the change was her own fault, and in this he was right.[42]