Fleet Air Arm bureaucracy and the missing 4.5-inch gun

If the Royal Navy knew the 4-inch gun was better for anti-aircraft fire, why were destroyers planned around the unfinished 4.5-inch mount?

The 4.5-inch mount promised one general-purpose battery for surface and anti-aircraft work, but its upper-deck version was not ready when war began, so the Navy had to keep mixed armament.

The 4-inch gun offered better anti-aircraft performance, while the planned 4.5-inch mount promised a general-purpose battery for surface and air targets. Advice from the Air Ministry's political administration differed from the experience of RAF personnel who flew and operated aircraft. Fleet Air Arm arrangements compounded that separation: the Navy supplied the money, while another ministry controlled important personnel decisions and equipment choices. Each ministry had its own priorities, and equipment failures readily became disputes over responsibility. Even well-intentioned decisions could provoke resentment when the service paying for an essential capability could not control it. The missing upper-deck 4.5-inch mount ultimately forced the Navy to retain mixed armament and revise the way it organized its destroyers.