The River class was a class of 151 frigates launched between 1941 and 1944 for use as anti-submarine convoy escorts in the North Atlantic. The majority served with the Royal Navy and Royal Canadian Navy (RCN), with some serving in the other Allied navies: the Royal Australian Navy (RAN), the Free French Naval Forces, the Royal Netherlands Navy and, post-war, the South African Navy. The first orders were placed by the Royal Navy in 1940, and the vessels were named for rivers in the United Kingdom, giving name to the class. In Canada, they were named for towns and cities, though they kept the same designation. Originally called a "twin-screw corvette", the name "frigate" was suggested by Vice-Admiral Percy W. Nelles of the Royal Canadian Navy. Canada originally ordered the construction of 33 frigates in October 1941. The design was too big for the locks on the Lachine Canal so it was not built by the shipyards on the Great Lakes and therefore all the frigates built in Canada were built in dockyards along the West Coast or along the St. Lawrence River below Montreal. In all, Canada ordered the construction of 70 frigates, including ten for the Royal Navy, which transferred two to the United States Navy. Twelve were built in Australia for the RAN (four to a modified design). After World War II, they found employment in many other navies the world over; several RCN ships were sunk as breakwaters. One, , was purchased by Aristotle Onassis and converted into the luxury yacht . Design The River-class ships were designed by naval engineer William Reed, of Smith's Dock Company of South Bank-on-Tees, to have the endurance and anti-submarine capabilities of the sloops, while being quick and cheap to build in civil dockyards using the machinery (e.g. reciprocating steam engines instead of turbines) and construction techniques pioneered in the building of the s. Its purpose was to improve on the convoy escort classes in service with the Royal Navy, including the Flower class. Improvements over the corvette design included markedly better accommodation. The twin engines gave only more speed but extended the range of the ship to nearly double that of a corvette to at . Among other lessons applied to the design was armament better designed to combat U-boats, including a twin mount forward and 12-pounder () aft. Fifteen Canadian frigates were initially fitted with one gun forward