A Royal Navy jump to 16-inch guns reshapes treaty arithmetic

What changes if the Royal Navy moves from 13.5-inch guns directly to 16-inch weapons before the First World War?

The ships become more costly, but the larger consequence is a much stronger British 16-inch battle line that the United States could not comfortably freeze in place through a naval holiday.

Adding an inch of calibre increases cost and industrial effort along the whole gun, not just at the muzzle. If the Queen Elizabeths, Renown, Repulse, and Hood all carried 16-inch weapons, Britain would possess thirteen such ships against the American Colorado force. That balance would undermine the familiar claim that the Colorados were comfortably superior to the Queen Elizabeth class. It could also make an early naval building holiday harder to sell in the United States, where political enthusiasm for a navy second to none was not matched by willingness to fund the necessary construction.