Seven miles to the north of Leicester, built on a steep and rugged hill, overlooking the river Soar, with a fair town and priory at its feet, the castle of Mount Sorrel, in the spring of 1217, frowned with feudal pride, and seemed to bid defiance to all comers. It was not, however, so impregnable as it looked, but had more than once changed hands during the terrible and sanguinary conflict then raging in England. However, the custody of Mount Sorrel was claimed as part of his inheritance by Sayer de Quency, Earl of Winchester, one of the twenty-five conservators of the Great Charter, and held by his deputy, Henry de Braybroke, in the interest of Prince Louis and the Anglo-Norman barons.
Mount Sorrel, however, was deemed a very important stronghold; and the Earl of Pembroke was anxious to gain possession of it for the king, with the object, as would appear from the result, of levelling it with the ground on which it stood. No sooner, therefore, did the protector’s truce with Louis expire, than Pembroke mustered an army, and, carrying the boy-king with him, marched to Mount Sorrel and laid siege to the castle, with such an appearance of determination to make himself master of the stronghold, that Henry de Braybroke, in great alarm, sent messengers to De Quency, declaring that, unless reinforced, he could not long hold out against such overwhelming odds.
On hearing that Mount Sorrel was invested by Pembroke, the Earl of Winchester went to Louis, and entreated him to send an army to relieve the fortress without delay; and the prince, who deemed it politic at the time to remain in the capital, summoned the Count de Perche, and entrusted him with the command of six hundred knights and twenty thousand men in mail--a force composed of Flemings, French, and Anglo-Normans--a large proportion being cavalry. Robert Fitzwalter, the Earls of Winchester and Hereford, William de Roos, William Beauchamp, William Moubray, with many other barons, accompanied the Count of Perche on his northward expedition, and the citizens of London manifested what zeal still existed among them for the invaders by furnishing funds to pay the cost of equipping so many warriors. It was thought that the Count de Perche and the Anglo-Norman barons were certain to strike a shattering blow at the royal cause, and Louis, on parting with the leaders of the enterprise, believed that he was simply sending them forth to put his enemies under their feet.