The base (often also colloquially referred to as HMS Eaglet) is also the home to a number of units, including: Royal Marines Reserve Merseyside, Naval Regional Command Northern England, Liverpool URNU, HMS Biter, HMS Charger, Sea Cadet Corps, and the Liverpool Royal Navy and Royal Marines Careers Office.

The Mersey Division of the RNVR was established in Customs House, Liverpool under the command of Edward Bootle-Wilbraham, 2nd Earl of Lathom in 1904, before moving to HMS Eagle (1804), a 50-gun frigate at Brunswick Dock, in 1911.

The ship was destroyed in a fire in 1926, and replaced by the First World War 24-class sloop HMS Sir Bevis, which was renamed Eaglet.

In 1971, the sloop was scrapped and HMS Eaglet moved ashore to a new HQ at Prince's Dock.

[1] The current stone frigate is based on Brunswick Dock in Liverpool, opened by the Duke of Edinburgh in 1998.