What if the Royal Navy had begun building heavily armed Battle-type destroyers in 1939?
Short answerThey would have been highly capable ships, probably evolving toward three twin 4.5-inch mountings with multiple pom-poms and torpedo tubes.
NotesThe proposed ship is recognized as an early version of the Battle-class idea and is judged potentially formidable. Once treaty limits disappeared, the answer suggests that the Royal Navy might have moved toward six 4.5-inch guns in three twin mountings, anticipating the later Daring pattern. It corrects the proposed light armament by noting that British 40 mm weapons of the period would be pom-poms rather than the later mix imagined in the question. The result would have been a powerful destroyer, but one whose fit reflected the weapons and mountings actually available in 1939.