Post WW1 was a troublesome time, the shortcomings of several capital ships had been exposed and new battleships and battle cruisers had to be designed & constructed plus now aircraft carriers plus the tactics to which they would be employed. The Royal Naval Air Service had been retained, but only just from the formation of the new RAF, another competitor for precious Treasury funding. The Royal Marines were now shouting above their place, no longer happy with manning ships guns, they were flying about in aeroplanes, driving armoured cars and playing soldiers in Russia, Somalia and other places.
The RNAS had managed to keep in their ranks Richard Bell Davis, Fredrick Bohill, Ray Collingshaw, William Dickson and Arthur Longmore among others and they with their former friends Oliver Locker Lampson MP, Murry Sueters MP, Winston Churchill and the Duke of Westminster were forming a powerful lobby group to persuade the Admiralty the future lay in naval aviation & not big gun capital ships.
The big breakthrough came with the Treaty in 1922. They Royal Navy could turn two of their new Invincible class battlecruisers into aircraft carriers. Since only two keels had actually been laid Sir Eustace Tennyson d'Enyncourt and his team had almost a clean sheet to begin with. Under Alan Payne the team designed a sleek 856' long ship. The Admiralty believed that no matter how big the defensive air group was enemy bombers would get through. Still clinging to the old two fleets rule gave the European threat of France & Italy so the battlefleet would be under threat from land based bombers so the all or nothing defences of the battle cruisers was continued. It was successfully argued that the air group was her primary weapon system so it was natural that the hanger should be protected as a magazine. The carriers had to not only survive a sustained heavy air attack, but had to be able to continue air operations after taking a large amount of battle damage.
A 527' long 12" belt protected the ships machinery with a further 4" plated double hull underneath. Bulk heads were 10" and a 6" sloped deck completed this enclosed space. Above this was a single 17'2" high 527' long and 71' wide hanger. Side protection was 4.5" and a 3.5" armoured deck was installed above. From the hanger to the stern & bows the deck was unarmoured, since it was considered that 500' was plenty of room to manoeuvre landing & launching aeroplanes.
Andrew Cunningham was given command of the Invincible with William Dickson command of the air group. Lumley Lyster got the Illustrious along with Arthur Longmore as air boss. The new First Sea Lord Leo Amery was so impressed with the design he actually wanted one for each of the battle squadrons.
Personally I would prefer the RN to lose one of the R class and keep Tiger instead.