The Q and R class was a class of sixteen War Emergency Programme destroyers ordered for the British Royal Navy in 1940 as the 3rd and 4th Emergency Flotilla. They served as convoy escorts during World War II. Three Q-class ships were transferred to the Royal Australian Navy upon completion, with two further ships being handed over in 1945. Roebuck had the dubious honour of being launched prematurely by an air raid at Scotts shipyard in Greenock, her partially complete hulk lying submerged in the dockyard for nine months before it was salvaged and completed.

The O and P class was a class of destroyers of the British Royal Navy. Ordered in 1939, they were the first ships in the War Emergency Programme, also known as the 1st and 2nd Emergency Flotilla, respectively. They served as convoy escorts in World War II, and some were subsequently converted to fast second-rate anti-submarine frigates in the 1950s.