They were considered capital ships by the terms of the 1922 Washington Naval Treaty and were included in the total amount of tonnage allowed to the Royal Navy.

They drew upon the experience gained by the Royal Navy since Furious had been designed and incorporated an island with a funnel, increasing their aircraft capacity by one-third and making it safer to land.

The first two ships of the class, Courageous and Glorious, spent the First World War on North Sea patrols, climaxing in the Second Battle of Heligoland Bight in November 1917.

[2] Furious had been fitted during the First World War with a flying-off and landing deck, but the latter proved largely unusable because of the strong air currents around the superstructure and exhaust gases from the funnel.

Her design was based on the very limited experience gained with the first two British carriers: Argus, less than three years old, and Eagle, which had carried out only 143 deck landings during preliminary sea trials in 1920.

This flight deck was not level; it sloped upwards about three-quarters of the way from the stern to help slow down landing aircraft, which had no brakes at the time it was designed.

Various designs for the flight deck were tested in a wind tunnel by the National Physical Laboratory which showed that the distinctive elliptical shape and rounded edges minimised turbulence.

This solution proved to be very unsatisfactory as it consumed valuable space, made parts of the lower hangar unbearable and interfered with landing operations to a greater or lesser degree.

The longitudinal arresting gear proved unpopular in service and it was ordered removed in 1927 after tests aboard Furious in 1926 had shown that deck-edge palisades were effective in reducing cross-deck gusts that could blow aircraft over the side.

[8] Furious's long exhaust ducting hampered landing operations, and restricted the size of the hangars and thus the number of aircraft that she could carry.

[14] No significant changes to the machinery were made during the conversion process to any of the three ships, but their increased displacement reduced their speed to approximately 30 knots (56 km/h; 35 mph).

[16] Furious retained ten of her original eleven breech-loading BL 5.5-inch Mk I guns, five on each side, for self-defence from enemy warships.

[22] During Furious's September 1930 – February 1932 refit, her anti-aircraft outfit was changed by the substitution of two 8-barrel 2-pounder pom-pom mounts for the forward 4-inch guns on the flying-off deck removed earlier.

Later testing proved that it was not deep enough to accomplish its task and that it lacked the layers of empty and full compartments that were necessary to absorb the force of the explosion.

During the Second World War, the carrier typically carried a single fighter squadron and two of strike aircraft of various types, although the mix was often adjusted for specific missions.

[38] The ship was reduced to reserve status on 1 July 1930 in preparation for a lengthy overhaul at Devonport from September 1930 to February 1932, focused on refitting her machinery and re-tubing her boilers.

She became a training carrier in December 1938 when Ark Royal joined the Home Fleet and continued on that duty until the start of the Second World War.

On 17 September 1939, U-boat U-29 struck the ship with two torpedoes, and Courageous became the first British warship sunk to enemy action in the Second World War.

[45] Force J, including Glorious, was organised to hunt for the German pocket battleship Admiral Graf Spee in the Indian Ocean.

[50] Captain Guy D'Oyly-Hughes requested and was granted permission to proceed independently to Scapa Flow in the early hours of 8 June.

On the way back across the North Sea, Glorious and her two escorting destroyers, Acasta and Ardent, were found by the two German battleships Scharnhorst and Gneisenau.

[52] The German heavy ships sank all three British vessels with most of their crews, although Acasta managed to torpedo Scharnhorst before she was sunk.

[55] Furious joined the Home Fleet off the coast of Norway on 10 April 1940 and her Swordfish made several attacks on German ships in Narvik on the following days.

On 1 July she escorted a convoy of Canadian troops bound for Iceland from Halifax and ferried over almost 50 aircraft, spare parts and munitions.

She reembarked her aircraft upon her arrival and made a number of air strikes on shipping in Norwegian waters and on the seaplane base at Tromsø through October 1940.

[58] Now with a new destination for her ferry trips, Furious transported two dozen Hurricanes to Gibraltar on 25 April where they were transferred to Ark Royal to be flown off for Malta.

[59] In July and August, Furious and Victorious attacked German installations in the Arctic areas of Norway and Finland with limited success and heavy losses.

[61] Providing cover for the Central Task Force, Furious's aircraft neutralised the airfields at La Senia and Tafraoui, both near Oran, Algeria.

In July the Home Fleet demonstrated off the coast of Norway in strength to distract attention from the Allied invasion of Sicily; Furious's role was to allow a German reconnaissance aircraft to spot the British ships and make a report then shoot it down.

[63] On 3 April 1944, Fairey Barracudas from Furious and Victorious attacked the German battleship Tirpitz in Altafjord, Norway, as part of Operation Tungsten.