Where Britain might have placed 18-inch coastal guns

How many 18-inch coastal batteries might Britain have built if its 18-inch/45 gun had worked?

Potential sites ranged from major British approaches to Singapore and Gibraltar, but the number would have depended on whether fixed defenses became more attractive than mobile fleet power under treaty limits.

Possible sites included the Strait of Dover, Plymouth, Portsmouth, the Thames, the Forth, Singapore, and perhaps Gibraltar. Mountings able to elevate toward 45 degrees would give the 18-inch gun the range needed to control broad approaches. Very heavy batteries could protect supply routes and enable the battle fleet, although Britain traditionally preferred the flexibility and imperial economics of mobile battleships over massive fixed fortifications. The treaty era could have made such defenses more attractive in imperial locations where new fortification remained permitted.