Nepean was one of the sixteen Admiralty M-class destroyers ordered by the British Admiralty in September 1914 as part of the First War Programme.[1] The M class was an improved version of the earlier L-class, required to reach a higher speed in order to counter rumoured new German fast destroyers. The remit was to have a maximum speed of 36 knots (67 km/h; 41 mph) and, although ultimately the destroyers fell short of that ambition in service, the extra performance that was achieved was valued by the navy. It transpired that the German warships did not exist.[2]
The destroyer had a length of 265 ft (80.8 m) between perpendiculars and 273 ft 4 in (83.3 m) overall, with a beam of 26 ft 8 in (8.1 m) and draught of 8 ft 11 in (2.7 m). Displacement was 971 long tons (987 t) normal.[3] Power was provided by three Yarrow boilers feeding Brown-Curtiss rated at 23,000 shaft horsepower (17,000 kW), driving three shafts and exhausting through three funnels. Design speed was 34 knots (63 km/h; 39 mph).[4]Nepean managed 33.88 knots (62.75 km/h; 38.99 mph) on 22,500 shp (16,800 kW) during trials.[5] A total of 228 long tons (232 t) of oil was carried. Design range was 2,530 nautical miles (4,690 km; 2,910 mi) at 15 knots (28 km/h; 17 mph), but actual endurance in service was less; sister shipMurray had a range of 2,240 nautical miles (4,150 km; 2,580 mi) at 15 knots (28 km/h; 17 mph).[3]
On 30 April 1917, the destroyer was the target of a torpedo launched by the German submarineUC-77.[14] It missed.[15] On 3 May, the destroyer formed part of the escort for the light cruisersDublin and Sydney, along with sister shipsObdurate, Pelican and Pylades, on a routine patrol of the North Sea. During the following day, they were attacked by the ZeppelinL 43.[16] The airship bombed the British ships, causing minor damage to Obdurate but otherwise causing no harm.[17] During the attack, the destroyer had identified a torpedo attack from German submarines.[16] Increasing activity from submarines against merchant shipping had led to the creation of a convoy system relying on destroyer escorts.[18] The flotilla was called upon to accompany over 26 vessels a day.[19] On 16 October, the destroyer joined with 53 other destroyers and 27 lights cruisers in an unsuccessful search for an escorted German minelayer.[20] At the same time, German cruisers attacked a convoy crossing to Scandinavia. The loss of nine merchant ships and three escorts led to the Admiralty increasing the escort to nine M-class destroyers.[21] During the following month, from 16 November, the destroyer formed part of the escort for the First Battlecruiser Squadron, led by Lion, which left Rosyth to attack German minesweepers.[22]Nepean did not take part in the subsequent Second Battle of Heligoland Bight, which involved large numbers of ships from both sides.[23]
At the end of the war, Nepean was part of the Fourth Destroyer Flotilla based at Devonport.[24] After the Armistice that ended the war, the Royal Navy returned to a peacetime level of strength and both the number of ships and personnel needed to be reduced to save money.[25] The destroyer was transferred to reserve at Nore.[26] However, the harsh conditions of wartime operations, particularly the combination of high speed and the poor weather that is typical of the North Sea, exacerbated by the fact that the hull was not galvanised, meant that the ship was soon worn out.[27]Nepean was declared superfluous to operational requirements, retired, and, on 15 November 1921, was sold to Cashmore of Newport, Wales, and broken up in 1923.[11]
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McBride, Keith (1991). "British 'M' Class Destroyers of 1913–14". In Gardiner, Robert (ed.). Warship 1991. London: Conway Maritime Press. pp. 34–49. ISBN978-0-85177-582-1.