British studies for 18-inch and 22-inch naval guns

What were the largest guns Vickers and Armstrong were considering in the 1920s?

A 22-inch/45 study, renewed consideration of 20-inch guns, and an 18-inch/56 proposal around 1921-23.

Vickers and Armstrong considered a 22-inch/45 gun in the 1920s, revisited a 20-inch weapon, and discussed an 18-inch/56 around 1921-23. These are design studies, with no claim that the weapons entered service. The Royal Navy repeatedly favored 45-caliber guns because longer barrels increased wear and the frequency of relining. Supporting them across a worldwide fleet would require more maintenance infrastructure and expense. Longer guns remained technically interesting, but their performance had to justify the overseas support burden.