The last stage of the siege had now been reached. By capturing the Picurina on its commanding knoll, the British had established themselves within 400 yards of the Trinidad and 450 yards of the Santa Maria bastions, which they could batter with every advantage of slope and ground. But it was a very costly business to make the necessary lodgement in the ruined fort, to demolish it, and throw its earth in the reverse direction, and to build in its gorge the two batteries (nos. 8, 9), which were to breach the body of the place. The fire of three bastions bore directly on the spot where the batteries were to be placed, and there was also a most deadly enfilading fire from the high-lying Castle, and even from the distant San Cristobal. Though the three batteries in the flat ground (to which a fourth was presently added) endeavoured to silence this fire, they only succeeded in doing so very imperfectly, for the French kept replacing one gun by another, from their ample store, when any were disabled. From the 26th to the 30th four days were employed in building the Picurina batteries, with great loss of life all the time, which fell mainly on the engineer officers who were directing the work and on the sappers under their orders. The French covered the whole of the Picurina knoll with such a hail of projectiles that no amount of cover seemed to guarantee those labouring in it from sudden death. When the batteries had been completed, the bringing forward of the guns and the ammunition cost many lives more. Twice there were considerable explosions of powder, while the magazines in the batteries were being filled.