She was built by Laird, Son & Company at their Birkenhead shipyard as one of six Earnest-class destroyers ordered as part of the Royal Navy's 1895–1896 construction programme, which were later classified as members of the B-class.

Earnest was ordered on 23 December 1895 as the first of six 30-knotter destroyers programmed to be built by Lairds under the 1895–1896 shipbuilding programme for the Royal Navy.

Like the other Laird-built 30-knotters, Locust was propelled by two triple expansion steam engines, fed by four Normand boilers, rated at 6,300 ihp (4,700 kW), and was fitted with four funnels.

[8] She was transferred to the Mediterranean Squadron in September 1898,[1] and was in August 1901 recommissioned at Malta as tender to the battleship HMS Caesar.

[1] Earnest was a member of the Eastern group of destroyers based at Harwich in 1908, entering refit at Chatham Dockyard in September that year.

[13] On 30 August 1912 the Admiralty directed all destroyers were to be grouped into classes designated by letters based on contract speed and appearance.

[29] She remained part of the Irish Sea Hunting Flotilla at the end of the war in November 1918, and was based at Kingstown (now Dún Laoghaire) in the South of Ireland.