The A class as designated in 1913 was a heterogeneous group of torpedo boat destroyers (TBDs) built for the Royal Navy in the mid-1890s. Some 42 vessels were constructed to the individual designs of their builders to meet Admiralty specifications, the only uniting feature being a specified top speed of 27 knots (50 km/h). In fact the initial six vessels were generally differentiated by a slightly lower speed and were often referred to as "26-knotters" to distinguish them from the following batch of thirty-six vessels; all fifteen surviving "27-knotter" vessels were classified by the Admiralty as the A class in 1913 to provide some system to the naming of HM destroyers. All of the "26-knotters" and most of the "27-knotters" had been lost or scrapped before the 1913 classification, but for convenience all 42 ships are listed below. The number of funnels varied from one to four. All vessels had a distinctive "turtleback" forecastle that was intended to clear water from the bow, but actually tended to dig the bow in to anything of a sea, resulting in a very wet conning position.

The B class as designated in 1913 was a heterogeneous group of torpedo boat destroyers (TBDs) built for the Royal Navy in the late 1890s. They were constructed to the individual designs of their builders to meet Admiralty specifications, the uniting feature being a specified top speed of 30 knots (56 km/h) and four funnels, although the funnel spacings differed between ships. All "30 knotter" vessels with four funnels were classified by the Admiralty as the B class in 1913 to provide some system to the naming of HM destroyers. At the same time all "30 knotter" vessels with three funnels were classified by the Admiralty as the C class and those with two funnels became the D class.