Centurion-class battleship

The four 32-calibre, breech-loading 10-inch Mk III guns of the main battery were mounted in two twin-gun, circular barbettes, one forward and one aft of the superstructure.[4] These barbettes were the first ones in the Royal Navy to be capable of loading at all angles of traverse and thus were circular rather than pear-shaped like those on the Royal Sovereigns and earlier battleships, which saved a considerable amount of weight. A steam engine was fitted to allow the gun turntable to traverse at one revolution per minute, but it proved too weak in service to completely stop the mounting in one place and tended to creep. The turntable could be rotated manually by a system of gears, but it was completely inadequate to the task. Maximum elevation was +35°, although a small piece of armour had to be removed to prevent the recoiling guns from striking it. The guns were hand-cranked up and down, although Barfleur was equipped with Siemens electric motors as an experiment that could move the guns through their full range of elevation in 14 seconds.[2][7][8] The Mk III guns fired shells that weighed 500 pounds (230 kg) with a muzzle velocity of 2,040 ft/s (620 m/s) that had a maximum range of 10,100 yards (9,200 m) when fired at an elevation of +12°05'. When raised to their maximum elevation, the guns could only be fired with a half-load of propellant, which gave them a muzzle velocity of 1,393 ft/s (425 m/s) and a range of 11,522 yards (10,536 m).[9]

Their secondary armament consisted of ten 40-calibre quick-firing (QF) 4.7-inch guns in single mounts. Half a dozen of these guns were mounted on the upper deck, protected by gun shields, and the remaining guns were mounted in casemates in the sides of the hull.[4] They fired a 45-pound (20 kg) shell at a muzzle velocity of 2,125 ft/s (648 m/s).[10] Defence against torpedo boats was provided by eight QF six-pounder, 2.2-inch (57 mm) guns[Note 1] and a dozen QF three-pounder (1.9 in (47 mm)) Hotchkiss guns.[4] These latter guns fired a 3-pound-3-ounce (1.4 kg) shell at a muzzle velocity of 1,867 ft/s (569 m/s).[12] The ships were also armed with seven 18-inch[Note 2] torpedo tubes, two on each broadside and one in the stern above water and one on each broadside underwater.[4]

The Centurion-class ships were mostly fitted with compound armour although some portions were made from improved Harvey armour. Their waterline main belt ranged in thickness from 9 to 12 inches (229 to 305 mm) although the bottom edge was 8 inches thick. It was 200 feet (61.0 m) long amidships and 7 feet 6 inches (2.3 m) high of which 5 feet (1.5 m) was below the waterline at normal load. Fore and aft oblique bulkheads, 8 inches thick, connected the belt armour to the barbettes to form the armoured citadel. The upper strake of 4-inch (102 mm) Harvey armour was above the waterline belt and 7 feet 6 inches high. It covered the ships' side between the rear of the barbettes up to a height of 10 feet (3.0 m) above the waterline. Oblique bulkheads of Harvey armour 3 inches (76 mm) thick connected the upper armour to the barbettes.[4]

The armoured deck lay across the top of the waterline belt and consisted of 2 inches (51 mm) of mild steel. Below the waterline, the 2.5-inch (64 mm) lower deck extended from the 5-inch (127 mm) bases of the barbettes to the bow and stern. Above the main deck the barbettes were 9 inches thick and 8 inches thick between the main and lower decks. The Centurions were the first British battleships to be fitted with an armoured hood or gunhouse above the barbettes. This was required to protect the large gun crews required to manually work the guns and consisted of 6 inches of nickel steel, although a portion of the rear had to be left open to work the guns.[13] This was the first step in the evolution of the modern gun turret.[14] The casemates for the 4.7-inch guns consisted of 4-inch faces and 2-inch sides of Harvey armour.[15] The sides of the forward conning tower were 12 inches thick while those of the aft conning tower were only 3 inches in thickness.[16]

Barfleur at anchor, after 1904

The Centurions had always been criticised for their weak secondary armament and a report by Captain John Jellicoe (captain of Centurion) in June 1901 advocated replacing the 4.7-inch guns with 6-inch guns and the removal of all of their above-water torpedo tubes. The Admiralty agreed with his proposal and plans were quickly drawn up. The BL 6-inch Mk VII gun replaced the smaller guns on a one-for-one basis. They were mounted in four double and two single casemates, six guns on the main deck and four on the upper deck. They were protected by 5-inch casemates of Krupp cemented armour that required the middle section of the superstructure to be rebuilt to accommodate them. To compensate for the additional weight, the aft bridge and the above-water torpedo tubes were removed and the foremast was replaced by a smaller signal mast. In addition a radiotelegraph was fitted. The net increase was only 78 long tons (79 t), although this was enough to slightly reduce their speed to about 16.8 knots (31.1 km/h; 19.3 mph). The reconstruction cost approximately £125,000.[17][Note 3]

Drawing of Centurion at sea

Centurion was the first of the sisters to be completed and she became flagship of the China Station in 1894. Barfleur was assigned to the Mediterranean Fleet in 1895, and in February 1897 she became part of the International Squadron, a multinational force made up of ships of the Austro-Hungarian Navy, French Navy, Imperial German Navy, Italian Royal Navy (Regia Marina), Imperial Russian Navy, and Royal Navy that intervened in the 1897–1898 Greek Christian uprising against the Ottoman Empire′s rule in Crete.[21] She joined her sister on the China Station in 1898 and became the flagship of the station's second-in-command. During the Boxer Rebellion in 1900, both ships contributed landing parties to participate in the Battles of the Taku Forts and of Tientsin.[22]

The sisters returned home in 1901 and Centurion began her reconstruction that lasted until 1903. Barfleur was briefly placed in reserve in 1902 before she began her reconstruction later that year. Centurion rejoined to the China Station in 1903 and sailed for home in 1905 after the renewal of the Anglo-Japanese Alliance eliminated any need for British battleships in the Far East. Barfleur returned to reserve after her reconstruction was completed in 1904, although she did participate in that year's manoeuvres. The following year, the ship was briefly recommissioned to take a replacement crew to the Far East and then became flagship of the Portsmouth Division of the Reserve Fleet upon her return. She was joined in that unit by Centurion when she arrived in 1905. The sisters remained in reserve until they were listed for sale in 1909 and sold for scrap the following year.[22]