Fitting triple turrets into existing ships

Could the Queen Elizabeth and Revenge classes have accepted triple turrets?

Possibly, but turret-ring and beam limits would probably require smaller guns; a triple mounting rarely fits a twin ring at the same caliber.

The controlling factors are turret-ring diameter, beam, and how much the opening can be enlarged. A triple mounting of the same caliber will rarely fit directly into a ring designed for twin guns. As a rule of thumb, the caliber usually has to fall, with a fifteen-inch twin potentially becoming something closer to a thirteen-and-a-half-inch triple. Tiger adds another constraint: very fast automatic mounts also need unobstructed training arcs around the superstructure.