Clifford’s Fort was originally built as a smooth bore coastal defence battery. Initial work on the Submarine Mining Establishment commenced in December 1885 and concluded in June 1886. The Test Room and Observing Station were built between June and October 1888.
The 6-pdr Q.F. Battery to protect the minefield was built between 17th and 31st September 1895.
The Submarine Mining Establishment was built within the boundary walls of the Clifford’s Fort, but much of it has now been built over and lost. The building associated with the mines were concentrated on the Eastern half of the complex.