The Fort itself
Grenville started out as a rough-stone bulwark, thrown up in haste in the early 1770s as part of the militia (temporary army) works to defend the Dockyard. The next phase was the rapid rebuild of the site to a much higher standard in the 1790s, when the main stonework and the brick-arched roofs were added. You can clearly see the join between these two phases, in the right-hand moat as you look at the main gate from outside. The higher-quality newer stonework finishes and the older, rougher work can be seen to underlie part of it.
The fort was staffed by artillerymen up to around 1820, we think - though there is some unceertainty about this. It was then abandoned, only to be re-opened and rebuilt again during the worries over the aggression of Napoloeon III, in the 1870s. This was the time when the fort reached its current appearance, with the building of the ugly concrete installations overlooking the bay.
The Palmerston-era concrete