The British had stolen a march on the world with the Dreadnought. The next step was to upgrade the Armoured Cruiser in the same way. News was leaked to the world that the new class would follow the Dreadnought but with 9.2" guns. As it turned out the Germans had the Blucher type into production with their superior 8.2" guns aboard before they got the real news of the Invincible class with eight twelve inch. The original Invincible / Indefatigable classes had a set of 12" guns in a very unwieldly lozenge arrangement. It was supposed to allow the central turrets to fire to each side but in practice this damaged the ship more than the enemy. There was enough time between the Dreadnought and Invincible for the Royal Navy to learn of the US Navies South Carolina superimposed armament and follow it with the battlecruisers.
This gives a much better balanced set of ships. The two Australis ships are built to a different layout to make up the six ships built. (see HMAS Tasmania.)
The first pair are laid down in 1905 with one more, each, in 1906 and 1907. These were big and fast ships for the time. The eight inches of side armour was supposed to be 8.2" and 11" German shell proof. The dozen single four inch were for use against destroyers, as it was thought the main armament would be used against any ships above that size, in a battle of the scouts.
I was not too impressed with my first try, above, for a Commonwealth first battlecruiser. The Indomitable above looks too modern, so I will see if I can age it a bit.
While the drawings are marked 'as completed', some of the 3" low angle guns were replaced with 3" AA guns in 1916-17 to eventually have 6x3" AA and 4x3" LA.
