Topweight, crew, and ammunition limited Audacious-class anti-aircraft armament

Why did the Audacious class begin with a limited 4.5-inch and pom-pom anti-aircraft battery?

Topweight was only one constraint; each additional gun also demanded crew, ammunition, stowage, and supply arrangements within a carrier designed before the war.

Topweight was only the first constraint because manpower and logistics also shaped the battery. Guns consume deck space, magazines, handling systems, and the people needed to operate them. The original design must be judged against the expectations and threats present when it was created.