The War Emergency Programme destroyers' were 112 destroyers built for the BritishRoyal Navy during World War II. They were based on the hull and machinery of the earlier J, K and N class destroyer. Due to supply problems and the persistent failure by the Royal Navy to develop a suitable dual-purpose weapon for destroyers, they were fitted with whatever armament was available. Recent advances in radar and weaponry were incorporated as they came available. As a result they were a relatively heterogeneous class incorporating many wartime advances, but ultimately based on a hull that was too small and with an armament too light to be true first-rate vessels equivalent of their contemporaries. As such they are often described as "utility" destroyers. It was not until the Battle class destroyer of 1944 that the Royal Navy returned to building larger destroyers. Many vessels were transferred to friendly navies.