They were derived from the preceding Flower-class sloop, but designed to appear double-ended.

Twenty-four ships to this design (hence the class name) were ordered between December 1916 and April 1917 under the Emergency War Programme for the Royal Navy in World War I, although two of them were cancelled before launch.

All were named after famous racehorses (winners of The Derby), but they were not named Racehorse class as the Admiralty realised that this could easily be confused in communications with the Racecourse class of paddle minesweepers, and they officially became the 24 class.

However, they had identical deckhouses and gun shields at either end of the vessel, with straight stems and sterns.

The symmetrical design was completed with fake anchors at the stern to confuse enemy targeting.