A 16.5-inch naval gun in 1902

What if a practical 16.5-inch naval gun had appeared in 1902?

It could arm British capital ships and accelerate rival heavy-gun development, bringing the move to larger, all-big-gun ships forward.

The scenario assumes that Elswick constructs and tests a 16.5-inch, 45-calibre gun in 1902. It could become the main weapon of a Lord Nelson-type ship or an earlier design, and later of Dreadnought. Rival navies would face pressure to develop larger guns. The increased cost and space demanded by those weapons could also accelerate the move to larger ships. A Dreadnought-type vessel might consequently be ordered around the time of the Lord Nelsons, or earlier.