Laid down in 1912 as HMS Dragon, the ship was renamed in 1913 under an Admiralty order to become one of the first alphabetical class destroyers.

[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.

[7] The ship was renamed Lookout by Admiralty order on 30 September 1913, joining what was to be the first class that were all received names that started with the same letter of the alphabet.

The airship called out a seaplane, which dropped bombs on the warships without damage, the aircraft escaping before the ships' anti-aircraft guns could start firing.

[20] On 16 August, the destroyer formed part of the escort for the Second Light Cruiser Squadron, which was itself protecting the minelayer Princess Margaret on a mission to lay a minefield in the North Sea.

On 20 March, Lookout was part of a flotilla supporting an attack from the air on the Zeppelin hangars in Zeebrugge from the seaplane carriers Riviera and Vindex.

[25] The flotilla attacked the German ships the next day; Lookout again took a peripheral role in the action and remaining unscathed.

[26] To combat the increasingly successful German U-boats, the Royal Navy looked to introduce convoys of merchant ships protected by warships.

After some initial success in the North Sea in March, April and May 1917, it was decided to extend the programme to the Atlantic Ocean.

However, on 7 July, when returning from convoy duty, Lookout spotted the German submarine UB-61 and attacked with depth charges.

[32] 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.