The "Illustrious" Class ships were the radical next generation of aircraft carrier which the Admiralty took steps to develop in 1935. They were to have a hangar protected against 500lb bombs and 6" shells with armouring to the flight deck. The flight deck between the lifts was 3" thick and the hangar walls, like the side belt, were 41" thick. As 5000 tons of armour had to be worked into a treaty limit of 23,000 tons, Illustrious was consequently considerably shorter than Ark Royal, and because the flight deck armour weighed 1500 tons, the second hangar deck was omitted to reduce the freeboard by 22 feet and preserve stability.
Illustrious was the first aircraft carrier to have an armour plated deck, she joined the Mediterranean fleet in September 1940, its aircraft had succeeded in crippling nearly half the Italian Navy, the biggest success for the Illustrious came in November when the Carrier's Swordfish torpedo bombers raided Toronto Harbours , in a couple of hours they managed to hit and severely damage three Italians battleships, two cruisers, two fleet auxiliaries and destroyed a fuel dump and several stores, Illustrious had had a busy time in the Mediterranean, its aircraft, equipped with long range fuel tanks carried out constant attacks on Axis shipping, airfields and supplies to the Africa Corps.
The first HMS.Illustrious, a third rate 74 gun frigate was launched at Buckler's Hard in 1789 and saw action against the French off Toulon in 1793 and Genoa in 1795, In the latter action she was instrumental in capture of two enemy war ships but suffered severe damage, and under tow was driven ashore by violent storm and abandoned after being set ablaze.
Illustrious or “Lusty” as she is fondly know to her crew was built at Swan Hunter on the Tyne and subsequently commissioned in her base port of Portsmouth in 1 982.
Having recently completed an intense training and assessment period, and taken a lead role in the Trafalgar 200 and International Festival of the Sea celebrations, Illustrious has assumed the responsibilities and duties of the Royal Navy ’s Fleet Flagship.