Why statutory fleet minimums cannot guarantee usable ships

What if Britain passed a law in 1997 preventing a ship's retirement until its successor was fully commissioned?

The rule would change the political debate but remain vulnerable to repeal, reserve-status loopholes, capability substitution, and the difference between legal hull counts and available ships.

A later Parliament could repeal the proposed replacement rule. A government could also retain an inactive ship alongside or claim that one new vessel replaced several older hulls. Requiring repeal would create another political obstacle to cuts, although a large parliamentary majority could overcome it. Linking minimum strengths for the army, navy, and air force is suggested as a way to give all three services an interest in defending the same rule. Legal hull totals would still differ from deployable capacity. Greater capability also cannot put one ship in several places at once.