To restore stability, the first 23 Hunts, including Cottesmore, were modified by removing a twin 4-inch mount, cutting down the ships' superstructure and adding ballast.

[2][12] On commissioning, Cottesmore joined the 21st Destroyer Flotilla, based at Sheerness and employed on escorting convoys along the East coast of Britain, together with patrol duties and support for minelaying operations.

[13] On 28 July Cottesmore and sister ship Calpe engaged German patrol boats off Cap de la Hague.

[13] On the night of 13/14 October 1942, Cottesmore formed part of a large force of Hunt-class destroyers (also including Albrighton, Eskdale, Glaisdale and Quorn) and eight Motor Torpedo Boats sent to stop the German auxiliary cruiser Komet, which was attempting to break out into the Atlantic in order to raid Allied shipping.

[17] On 6 June 1944, Cottesmore took part in the Allied invasion of Normandy, escorting minesweepers to Gold Beach and then providing gunfire support to the landings.

[13][18] Following the initial landings, she remained on duty in the Channel until August, patrolling off the beaches to prevent attacks by German torpedo boats and midget submarines, and escorting reinforcement convoys.

In November 1944, Cottesmore and sister ship Garth escorted the monitors Erebus and Roberts when they bombarded Walcheren during Operation Infatuate, the British landings on the island.

On 20 April 1950, the ship was sold to Egypt, and was renamed Ibrahim El Awal on 17 July 1950, and entered refit at the J. Samuel White shipyard at Cowes.