St. Catherine’s Fort was built between 1867 and 1870 on a small island just off Tenby. The wide flat beaches at Tenby had been identified as a possible landing place for a hostile force attacking Milford Haven from the land side.
The Fort in rectangular in shape and of two storeys. The gateway is covered with a flanking gallery on each side and rows of loopholes. The ground floor has the magazines and six 7-inch RML guns in casemates with iron shields. With three guns on each side, these covered the north and south beaches at Tendby. The top floor was built to mount three 9-inch RML guns in barbette mounts, although it appears that only two were ever mounted.
In 1892 two of the three 9-inch RML’s guns were removed (20th September). By 1900 the fortifications does not appear to have been armed.
A 5-inch gun was later mounted on a lower platform, and this location was then used for a 40mm Bofors gun in World War 2.