The I-class ships were improved versions of the preceding H-class. They displaced 1370LT at standard load and 1888LT at deep load. The ships had an overall length of 323feet, a beam of 33feet and a draught of 12feet. They were powered by two Parsons geared steam turbines, each driving one propeller shaft, using steam provided by three Admiralty three-drum boilers. The turbines developed a total of 34000shp and were intended to give a maximum speed of 35.5kn. Icarus reached a speed of from during her sea trials.[1] The ships carried enough fuel oil to give them a range of 5500nmi at . Their crew numbered 145 officers and ratings.[2]
The ships mounted four 4.7-inch (120 mm) Mark IX guns in single mounts, designated 'A', 'B', 'X' and 'Y' from bow to stern. For anti-aircraft (AA) defence, they had two quadruple mounts for the 0.5 inch Vickers Mark III machine gun. The I class was fitted with two above-water quintuple torpedo tube mounts amidships for 21inches torpedoes.[3] One depth charge rack and two throwers were fitted; 16 depth charges were originally carried,[2] but this increased to 35 shortly after the war began.[4] The I-class ships were fitted with the ASDIC sound detection system to locate submarines underwater.[5]
The ship was ordered under the 1935 Build Programme from Hawthorn Leslie, Hebburn, on 30 October 1935 with a delivery date of 30 April 1937. The ship was laid down on 26 January 1936 and launched on 11 December the same year, and was the first RN warship to carry the name. Imperial was completed late, on 30 June 1937, after a delay in the delivery of the gun mountings. The contract price was £257,117 excluding items supplied by Admiralty such as guns and communication equipment.[6]
Imperial took part in the Norwegian Campaign and in August 1940 was redeployed to escort convoys to Malta. On 28 May 1941, Italian bombers from 41 Gruppo attacked Imperial and inflicted severe damage. Once it was ascertained that the vessel was damaged beyond repair, she was scuttled 55nmi east of Kassos.