|The Admiralty held a Cruiser Conference in 1929 and the subject of an intermediate cruiser design was a big topic. What was desired was a cruiser smaller than the Leander, ranging in the 4,000-5,000-ton displacement range. However, the design would
still have to have the ability to function with the fleet and on trade protection missions. Resulting from this desire, different designs were drawn, some with 6-inch guns and some with 5.5-inch guns. Some with single gun mounts and some with twin gun
mounts. Economy was critical because more of the smaller cruisers could be built for the same amount of fewer Leanders. The displacement and costs of the Leanders had crept upwards significantly during their design and construction. Further, it was
difficult for the Admiralty to squeeze a Pound from the Labour government and the intermediate cruiser would certainly cost less. Another factor was the desire of some Admirals to have a small cruiser that could function as a destroyer leader. Not only
would it have to have the speed of a destroyer but also it had to have the same acceleration capability of destroyers. A typical cruiser were much slower in accelerating compared to a destroyer.
Since the design had to serve as a trade cruiser as well as a fleet cruiser and destroyer leader, range was an important consideration in the trade protection mission. In this area there was not enough displacement available to give the design a true range of a
trade cruiser. As it was, the range was limited to 5,300 nm at 13-knots. In the Bismarck hunt the Galatea had to break off before her accompanying cruisers in order to refuel. Originally, the Admiralty was going to build at least eight in the class, Arethusa
in the 1931 program, Galatea in the 1932 program, three ships in the 1933 program and three ships in the 1934 program. However, events intervened. Japan announced a new light cruiser design with fifteen 6.1-inch guns on an alleged displacement of
8,500-tons. This would become the Mogami Class and of course Japan had grossly misstated the displacement by over 50%. The Admiralty properly doubted the stated characteristics but the press and public berated the current British designs of the
improved Leander and Arethusa. As a response two of the ships of the 1934 program were eliminated and only Penelope was built and two of three ships in the 1935 program were eliminated and only the Aurora was built. Instead of more Arethusas, the
Southampton or Town Class was developed and built.
The Arethusa Class displaced between 5,220 to 5,270-tons standard and 6,665 to 6,715-tons full load. Length was 506-feet (154.22m) overall and 480-feet (146.3m) between perpendicular bulkheads. Beam was 51-feet (15.54m) and draught 16-feet
6-inches (5.03m) mean depth. For Arethusa and Galatea the original armament was six 6-inch Mk XXIII guns mounted in three twin turrets, four single 4-inch Mk V guns, two quadruple 0.5-inch Vickers machine gun mounts, and six 21-inch torpedoes
mounted in two triple mounts. When it came to building Penelope and Aurora, twin 4-inch guns were used instead of single mounts. The class, except for Aurora, also carried a catapult and one aircraft, a Hawker Osprey, although the Admiralty tried
every which way to have two planes. There was no hangar facility. The power plant consisted of four Admiralty 3-drum boilers providing steam for four Parsons geared turbines, providing 64,000shp with a maximum speed of 32.25-knots. As mentioned,
range was 5,300 nm at 13-knots. The armor scheme had 2.25-inch belt protecting machinery spaces, 3-inch magazine sides, 2-inches magazine crowns and a 1-inch deck.