Why the Type 81 programme stopped at seven ships

The Type 81s were intended to take over the general-purpose and anti-submarine duties of Black Swan-class sloops and Loch-class frigates. They were originally ordered as sloops, then reclassified as second-generation frigates to maintain frigate numbers during the 1960s. More than twenty had been planned, yet only seven were built. Three survived the reduction largely because contracts for their complex machinery could not readily be cancelled. At roughly 2,300 tons standard and 2,700 tons fully loaded, they were only modestly larger than pre-war Tribal-class destroyers. The small production run and changed label shaped both programme economics and later judgements of the class.