They were laid down in the late 1930s as part of the rearmament of British forces in response to the emerging threats of Nazi Germany, Fascist Italy and Imperial Japan.

The Illustrious class followed the Yorktown but preceded the Essex, the latter being designed after the US abandonment of the Second London Naval Treaty and its tonnage limitations.

Pre-war doctrine held that the ship's own firepower, rather than its aircraft, were to be relied upon for protection, since in the absence of radar, fighters were unlikely to intercept incoming attackers before they could release their weapons.

The armament was similar to Ark Royal with twin 4.5 inch turrets (in a new "between-decks" or countersunk design) arranged on the points of a quadrant.

The guns were mounted sufficiently high so that they could fire across the decks; de-fuelled aircraft would be stowed in the hangar for protection during aerial attack.

Like their contemporary USS Enterprise, they fought a long and consuming war, and, despite significant overhauls and repair of battle damage, were worn out by 1946, and were scrapped in the mid-1950s.

Over eight years between 1950 and 1957 she was extensively rebuilt incorporating modern equipment (angled flight deck, steam catapults) to enable her to operate Cold War-era jet aircraft.

Although Victorious completed a refit in 1967, a minor fire with a manpower shortage and reduction in the naval budgets mean she was not recommissioned but retired in 1968 and sold for scrap.