While the Angevin host placed Wolvesey Castle under siege, Empress Matilda set up her headquarters in the royal castle and Robert of Gloucester established his command post near Winchester Cathedral (then Saint Swithun's). On August 2, the bishop's men set fire to Winchester, destroying a large part of the city. Wolvesey was a tough nut to crack. It was erected in 1138 and being in the corner of the city walls, could easily contact the outside world. Nevertheless, the Angevins put strong pressure on its defenders.