The class was designed to operate in close waters such as harbour approaches, shipping lanes, rivers and estuaries.

Together, the ships of this class formed the Royal Navy's Inshore Survey Squadron.

[1] The class consisted of three ships, and were of composite (wood on metal frames) construction.

They were modified, from plans loaned by the Port of London Authority who had already purchased HMS Polsham in 1967 and converted her to a survey vessel, Maplin.

The two vessels were renamed, Jonas Hanway and Earl of Romney, and were initially based and operated in conjunction with the Gravesend Sea School on the Thames at Denton.