The Prince’s Gallery was a short tunnel built about 1790 under a rock outcrop on the Northern Lines. This tunnel linked Castle Communication and Hanover Battery with the Prince’s Lines. Within this Gallery there is a entrance to a ramp that leads down to the Star Chamber. This ramp was primarily to assist in the movement of guns, ammunition, and other heavy equipment down to the King’s and Queen’s Galleries below.
An engine room was built in a chamber dug immediately off the Prince’s Gallery and adjacent to the aforementioned ramp down to Star Chamber in about 1900. This was primarily to power the Defence Electric Lines on the Northern Lines.