 As well as these fifty ships to the standard 'Admiralty' design, twelve more R class were designed and built by the two specialist builders Yarrow Shipbuilders and John I. Thornycroft & Company to their own separate designs.Three were ordered from Thornycroft and four from Yarrow in July 1915, and two from Thornycroft and three from Yarrow in December 1915.They were the last three-funnelled destroyers ordered by the Royal Navy (although commissioned in 1973 had three funnels, these were not all on the centreline).