The Washington Naval Treaty of 1922, signed by the Allied maritime powers, was intended to prevent a naval arms race similar to that which had precipitated the First World War. The treaty restricted the building of capital ships and limited heavy cruisers to a displacement of no more than 10,000 tons. A newly planned class of heavy cruisers to replace the Hawkins class were designed within the constraints of the Washington Treaty, to the maximum displacement and armed with 8in (203mm) guns. Christened the County class, the new cruisers were a fine balance of speed, firepower and excellent seahandling and were built in three sub-classes.
The first five Kent class cruisers, augmented by two further ships of the class for the Royal Australian Navy, were ordered in 1924, with four London class cruisers contracted the following year and two Norfolk Class vessels in 1926. Each sub-class were improved variants of their predecessor; however, their quality came at a cost of just over £2 million per ship at a time when British interwar military spending was in decline and the County class gave way to cheaper light cruiser designs as the likelihood of a second war approached. Despite the strain on Admiralty budgets, the ships represented good value for money and many underwent modernisation during the 1930s. As the Royal Navy’s most heavily armed cruisers, they played a crucial role in British maritime operations during the Second World War.