 Most were built to the design prepared by the Admiralty ("Admiralty S class"), finalized on 3 July 1917.As was common practice during the First World War, the Admiralty allowed two specialist destroyer builders, Thornycrofts and Yarrows a free hand to develop their own designs based on the current Admiralty designs, which other yards were contracted to build.Generally, these "specials" had considerably higher speeds; this performance enhancement stemmed largely from the higher quality of workmanship practiced by these specialist builders, rather than due to deficiencies of the Admiralty designs.