Laid down on 14 December 1912 as HMS Picton, the ship was renamed on 30 September 1913 under an Admiralty order to become one of the first alphabetical class destroyers, being launched on 30 October.

On commissioning, the vessel joined the Third Destroyer Flotilla and operated as part of the Harwich Force during the First World War.

Although subsequently offered for sale to the Finnish Navy, Llewellyn was instead withdrawn from service and sold to be broken up on 18 March 1922.

[1] The design followed the preceding Acasta class but with improved seakeeping properties and armament, including twice the number of torpedo tubes.

[4] Armament consisted of three QF 4 in (102 mm) Mk IV guns on the ship's centreline, with one on the forecastle, one aft and one between the funnels.

[9] Picton was ordered by the British Admiralty under the 1912–1913 Programme as part of a class of destroyers named after characters in Shakespeare's plays and the Waverley novels by Sir Walter Scott.

For example, the destroyer returned to Heligoland Bight to provide escort to British minelayers on 8 January, undertook sweeps for German submarines in the Irish Sea on 29 and 30 January, escorted troop convoys to France on 1 and 2 April and protected minesweepers working on Dogger Bank on 1 and 2 June.

[23] The ship spent much of the rest of the year on anti-submarine patrols and, on 4 December, unsuccessfully attacked the German submarine UB-18 with depth charges.

[25] On 17 March, the ship formed part of a flotilla including Laertes, Laforey and Paragon patrolling the Dover Barrage.

The German High Seas Fleet set out to destroy the ships but failed to find them and returned to their base without a shot being fired.

[28] After the Armistice of 11 November 1918 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.