Between 1966 and 1968, based in Mozambique, these ships were part of the Portuguese naval deterrent force against the Royal Navy Beira Patrol which was trying to enforce sanctions against Rhodesia.

A pair of Mark V "utility" mounts for twin 40 mm Bofors guns were sited amidships, each with its own predictive Simple Tachymetric Director (STD) for fire control.

These ships omitted the Mark V Bofors mounts and the aft 4-inch (10 cm) guns and had the superstructure extended to provide additional flag accommodation and stepped a tall mainmast.

The four other ships were completed as survey vessels, specifically to deal with the vast numbers of uncharted wrecks and mines around the British Isles from wartime.

They had shorter forward shelter decks and carried survey boats under davits abreast the funnel and minesweeping gear aft.