In the mid 1800's, the Royal Navy began to equip its larger men-of-war with so-called steam barges or steam pinnaces. After experiments with a number of different types, 30, 40, 50 and 56 ft boats became most widely used. By the end of the century, the first motor pinnaces were ready for duty. When the First World War broke our, however, steam boats returned to the scene. The 50 ft pinnace for 'HMS Renown' dates from this period. As many as 4 of these boats other man-of-war. The boats had a small forepeak, a crew compartment, a boiler room and a cabin. Above the crews' quarters was a conical steel base with a permanent universal ring, on which a 3-lb quick-firing cannon or maxim machine gun could be mounted.
This type of boat was used for a variety of tasks; ranking officers between boats, or to patrol the mouths of harbours for the protection of ships anchored therein hence the name 'picket boats