Shipyards started cutting steel for the first aircraft carrier before the design was finalised. This was done (according to some) to make it harder for the incoming Government to cancel the project.

They didn’t cancel the project and instead requested a major design change to support higher performance fighter planes (catapult instead of STOVL), only to reverse that decision when they saw the ultimate price tag. The result was the mother of all project change request queues.

Yeah, that project too was delayed a bit and went somewhat over budget