Recycled turrets could turn retired battleships into new Vanguards

Would the Royal Navy keep all of its older R-class and Queen Elizabeth-class battleships if war did not begin until 1942?

Probably not; Britain could accept a short-term reduction while reusing their turrets in new Vanguard-type hulls, then repeat the process across more older ships.

In the delayed-war scenario, the Royal Navy would not necessarily keep every older R-class ship simply because hostilities had not begun. Retiring one hull, removing its 15-inch turrets, and installing them in a new Vanguard-type battleship could justify a temporary reduction in numbers. Once the first conversion exposed the engineering problems, later ships could be prepared and supplied more efficiently in peacetime. The programme might eventually draw on both the R class and the least modern Queen Elizabeth-class ships, exchanging old hulls for a larger force of modern capital ships.