Over the next few years, and especially following the report on the Rock’s defences submitted in 1768 by the Chief Engineer of Gibraltar, William Green, the original wall was further improved. The sills of the embrasures were found to be too high for guns to cover the Inundation and the ground in front of King’s and Prince’s Lines, so they had to be lowered and the most easterly five splayed more to the right. Steps were cut to join King’s Lines so that the lines could be speedily reinforced. It was at this time that the St. Bernard’s Wall was renamed the Grand Battery.
B. Cornwell, who styled himself ‘a native of the garrison’ described the Grand Battery in length in his book ‘A Description of Gibraltar with an account of the Blockade, Siege, etc.’, published in 1782, almost at the end of the Great Siege (1779-1783). He wrote as follows:
‘The grand battery, on which a vast number of cannon are mounted, is a very strong and well-built fortification; the walls are 22 feet thick, and it is impossible for the fire of the enemy to touch any part of it but the very top of the merlins [i.e. merlon - resembling a tooth, it is the raised part of the parapet between two embrasures], the main wall being concealed and defended by the before-mentioned glacis (the glacis had a palisade in front of it and was mined underneath).
‘This great battery seems calculated entirely to oppose the enemy only in case of a storm [i.e. an attack], as the guns do not point to the Spanish lines, nor can be brought to bear on them; but it effectually commands the isthmus as far as the second garden, and would make a dreadful havoc among the Spaniards should they ever venture to approach any nigher [i.e. nearer] than they have already done. The guns on this battery are for this reason always kept charged with round and grape shot, and levelled just man-height from the surface of the isthmus; an artillery guard is also kept at the battery, and a lighted match constantly ready to apply to the cannon in case of necessity.
‘As it was observed that none of the guns of this great battery could clear round Forbes’s, which is at the east point of the Inundation, or scour the Prince’s Lines, a new one, very strong and well built, called the Cavalier [a work raised higher than the ramparts in order to command the surrounding countryside], was lately erected on a small bastion at the west end of it. This new battery is mounted with very heavy cannon, and would be very destructive to the enemy in case of a storm, as it would effectively flank them, while the former would destroy them in front.’