They were designed in 1778 by Sir John Williams in response to an Admiralty decision to discontinue 32-gun, 12-pounder (5.4 kg), vessels.

Initially intended for a crew of 260 this was increased to 270 when the secondary armament was boosted on 25 April 1780.

The second ship, ordered on 19 December 1780, had the position of its hawseholes changed to just above the cheeks.

This design modification carried over to the last two ships, requested between August and December 1781, which also had their lines slightly altered.

[3] The last to be built, HMS Romulus was ordered in December 1781[4] by which time, Williams' Latona-class frigate was in service, a 38-gun 18-pounder built to compete with Edward Hunt's Minerva-class.