The Vengeur-class ships of the line were a class of forty 74-gun third rates, designed for the Royal Navy as a joint effort between the two Surveyors of the Navy at the time. The Vengeur Class, sometimes referred to as the Surveyors' class of third rates, amongst other names, was the most numerous class of ships of the line ever built for the Royal Navy - forty ships being completed to this design. Due to some dubious practices, primarily in the commercial dockyards used for construction, this class of ships earned itself the nickname of 'Forty Thieves.'

A blockship is a ship deliberately sunk to prevent a river, channel, or canal from being used as a waterway. It may either be sunk by a navy defending the waterway to prevent the ingress of attacking enemy forces, as in the case of HMS Hood at Portland Harbour in 1914; or it may be brought by enemy raiders and used to prevent the waterway from being used by the defending forces, as in the case of the three old cruisers HMS Thetis, Iphigenia and Intrepid scuttled during the Zeebrugge raid in 1918 to prevent the port from being used by the German navy.