The artilleryman made several attempts, but each time missed the mark.

Colonel Southwell undertook the management of the mortar himself, and soon succeeded in dropping a shell upon the roof of the building, which proved, as he had suspected, to be in use as a magazine.

There was a tremendous explosion, the chapel was shattered into fragments, Caraccioli and three other officers were killed, and a great breach was blown in the main rampart.
A loud cheer broke from the besiegers, and Colonel Southwell at once put himself at the head of the men in the trenches and advanced to storm the breach before the enemy could recover from their confusion.

The disastrous effects of the explosion had, however, scared all idea of further resistance out of the minds of the defenders, who at once rushed out of the works and called out that they surrendered, the senior surviving officer and his companions delivering up their swords to Colonel Southwell, and begging that protection might at once be given to their soldiers from the Miquelets, whose ferocity was as notorious then as it was a hundred years afterward.
Peterborough appointed Colonel Southwell governor of Montjuich, and at once turned his attention to the city.

The brilliant result of the attack on the citadel had silenced all murmurs and completely restored Lord Peterborough's authority.