Would the treaties permit 15-inch/50 refits?

Could Britain legally refit its older capital ships with 15-inch/50 guns under the naval treaties?

It was arguable but uncertain: Britain could say the caliber and shell size were unchanged, while other powers could treat the longer weapon as a major upgrade.

Removing underwater torpedo tubes could free space and weight, while retired 15-inch/42 weapons might reinforce imperial coastal defenses. The difficult point was whether replacing existing guns with the longer 15-inch/50 counted as a prohibited major upgrade. Britain could argue that caliber and shell size remained unchanged even though the longer barrel increased performance. This creates a negotiable legal position rather than an obviously permitted refit, because treaty partners could reasonably focus on capability instead of nominal bore alone.