In 1917, Nepean formed part of the escort for the light cruisers Dublin and Sydney when they were attacked by the Zeppelin L 43 and the First Battlecruiser Squadron during the Second Battle of Heligoland Bight.

[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.

[8] Nepean was laid down by John I. Thornycroft & Company at their yard in Woolston, Southampton in February 1915, was launched on 22 January the following year and was completed three months later in March.

[15] On 3 May, the destroyer formed part of the escort for the light cruisers Dublin and Sydney, along with sister ships Obdurate, Pelican and Pylades, on a routine patrol of the North Sea.

[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.

[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.

[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.