While its exact function is not known, it probably served as a pele tower for the manorial complex (now demolished) in which it was situated.

The tower is the last remaining structure of a manorial complex whose surviving ruins were torn down with the expansion of Pembroke Dockyard in 1844.

[1] It received its name from the de Paterchurch family which originally owned the land.

[2] The land around the tower was purchased in 1759 by the Board of Ordnance to build an artillery battery to defend the interior of Milford Haven Waterway from attack.

The tower's rubble stone walls range in thickness from 2.5 to 4 feet (0.8 to 1.2 m).