What a treaty ban on submarines would change

How would a Washington treaty ban on submarines have changed the Royal Navy?

Probably not much; the Navy would still prepare for submarine warfare and retain suitable escorts even if construction were formally restricted.

Even if interwar negotiations had formally banned submarines, the Royal Navy would still have retained destroyers and sloops and continued thinking about anti-submarine precautions. The proposed ban also functioned as a budget strategy: removing a costly threat from the board would free resources, much as proposals to ban heavy bombers appealed to air ministries. Planners could not safely assume that such a prohibition would hold. The proposal shows how force-planning costs could shape an arms-control position.