The Lord Nelson class consisted of a pair of pre-dreadnought battleships built for the Royal Navy in the first decade of the twentieth century. Although they were the last British pre-dreadnoughts, both were completed and commissioned well over a year after had entered service in late 1906. and were assigned to the Home Fleet when completed in 1908, with the former ship often serving as a flagship. The sister ships were transferred to the Channel Fleet when the First World War began in August 1914. They were transferred to the Mediterranean Sea in early 1915 to participate in the Dardanelles Campaign.
They remained there after the end of that campaign in 1916 and were assigned to the Eastern Mediterranean Squadron, which was later redesignated the Aegean Squadron, to prevent the ex-German battlecruiser and her consort, the light cruiser , from breaking out into the Mediterranean from the Dardanelles, although neither ship was present when the German ships made that attempt in early 1918. Both ships participated in the Occupation of Constantinople in November following the Armistice of Mudros which ended Turkish participation in the war. The sisters returned home in mid-1919 and were placed into reserve upon their arrival. Lord Nelson sold for scrap in 1920, but Agamemnon was converted into a radio-controlled target ship that year and continued in that role until being sold for scrap in early 1927, the last surviving British pre-dreadnought.
Background and design
Pioneering naval gunnery developments by Captain Percy Scott in the early 1900s were already pushing expected battle ranges out to an unprecedented , a distance great enough to force gunners to wait for the shells to arrive before applying corrections for the next salvo. A related problem was that the shell splashes from the more numerous smaller weapons tended to obscure the splashes from the bigger guns. Either the smaller-calibre guns would have to hold their fire to wait for the slower-firing heavies, losing the advantage of their faster rate of fire, or it would be uncertain whether a splash was due to a heavy or a light gun, making ranging and aiming unreliable. Another problem was that longer-range torpedoes were expected to soon be in service and these would discourage ships from closing to ranges where the smaller guns' faster rate of fire would become preeminent. Keeping the range open generally negated the threat from torpedoes and further reinforced the need for heavy guns of a uniform calibre.
After being appointed Director of Naval Construction in early 1902, Philip Watts and the Third Naval Lord and Controller of the Navy, Vice-Admiral William May conducted studies that revealed the destructive power of smaller guns such as the was far smaller than that of larger guns like the . The greater damage inflicted at greater range by larger guns meant that there was a very real chance that the lightly protected smaller guns would be destroyed before they could open fire and that thicker armour was required over a greater area to resist large-calibre shells.
The Board of Admiralty wished to keep the size of the 1903–1904 Naval Programme battleships to about the of the earlier and also required them to be able to use the drydocks at Chatham, Portsmouth and Devonport, even though these had been enlarged before the ships were completed. This latter requirement severely constrained the length and beam of the design. Preliminary design work began in mid-1902 and it became clear that a displacement at least equal to that of the preceding would be required. Lacking a consensus on the design, May called a conference in November to discuss the way forward. The participants agreed to increase the armour to a maximum of 12 inches and the maximum displacement to , eliminated the three-calibre gun armament that had proven so unpopular in the King Edward VIIs in favour of a mix of 12-inch and guns, and rejected the version armed with only guns proposed by Watts.
The Admiralty formally approved a design armed with four 12-inch and a dozen 9.2-inch guns on 6 August 1903, but revoked it in October when they discovered that it could not be docked at Chatham. As it was now too late to revise the design in time for the 1903–1904 Programme, the Admiralty ordered three more King Edward VII-class ships instead. Watts refined the design to ensure that it could enter the Chatham docks, which required reducing the number of 9.2-inch guns to only 10, and it was approved on 10 February 1904. A planned third ship of the class was cancelled due to financial pressures arising from the purchase of the Swiftsure-class battleships.