They were intended to meet the threat of seabed mines laid in shallow coastal waters, rivers, ports and harbours, a task for which the existing ocean-going minesweepers of the Algerine class were not suited.

The design of the class drew on lessons learnt in the Second World War when it became apparent that minelaying in coastal waters was more effective than in the deep sea; the existing fleet minesweepers were not well suited to deal with this threat.

Design started at the Naval Construction Department in Bath in 1947 and the first ship was ordered in September 1950; the class eventually numbered 119 vessels.

[1] They were diesel powered vessels of 440 tons displacement fully laden, largely constructed from aluminium and other non-ferromagnetic materials, with a hull composed of a double layer of mahogany planking.

The contemporary but smaller inshore minesweepers were originally to be named after birds, but became the Ham class, after towns and villages ending in "-ham".

[1] Sixteen of the class were converted to minehunters[1] by the incorporation of active rudders and the installation of the Type 193 minehunting sonar and associated equipment, including a very welcome enclosed bridge, the exception being HMS Highburton which retained her open bridge until decommissioned in the 1970s, this actually becoming a source of pride for her crew when meeting other Ton crews.

These vessels, comprising HM Ships Beachampton, Monkton, Wasperton, Wolverton and Yarnton had their minesweeping gear removed and were fitted with a second Bofors 40 mm gun aft of the funnel.