Britain tested 20-inch guns but did not master production

Did the British armaments industry ever test a 20-inch naval gun?

It appears to have tested one, but not to have produced it reliably; claims about still larger guns remain uncertain because records are sparse.

Firing or constructing an experimental weapon differs from producing it reliably for service. Britain is said to have tested a 20-inch gun, while rumors from gun-forge traditions suggest Elswick may have attempted something still larger. Precise answers are difficult because relevant industrial and government records are incomplete. Caliber progressions also need not remain in a fixed 1.5-inch sequence once weapons become this large: the marginal difference between 19.5 and 20 inches may not justify avoiding the round-number jump. The surviving evidence illuminates both ordnance development and the limits of the archive.