This is the first study in depth of the Royal Navy's vital, but largely ignored small craft. In the age of sail they were built in huge numbers and in far greater variety than the more regulated major warships, so they present a particular challenge to any historian attempting a coherent design history. However, for the first time this book charts the development of the ancillary types, variously described in the 17th century as sloops, ketches, brigantines, advice boats and even yachts, as they coalesce into the single 18th-century category of Sloop of War.