Royal Navy response to evidence of Japan's A-150 battleship

What would Britain do if it obtained A-150 blueprints in 1937?

Blueprints alone change little, but proof of construction likely triggers crash redesigns of later battleships and larger armored carriers.

Blueprints alone would give Britain little reason to change its building programme; evidence that Japan was constructing the design would create a much more urgent threat. If that intelligence arrived in May 1937, Anson and Howe could change to another design, while Duke of York would already be too far advanced. An 18-inch battleship would be one option, while another would use the 16-inch gun under development in four quadruple turrets. The carrier response would push the Illustrious programme toward the larger, roughly 27,000-ton Implacable form. Such a programme would reflect contemporary confidence that battleships could defeat other battleships, alongside two decades of British concern about Japan and repeated confrontations between their naval forces.