The longer-ranged 4.5-inch weapon would remain formidable against German destroyers, so Narvik's basic shape may not change greatly. The larger difference appears in anti-aircraft arcs: HMS Gurkha would not need to leave formation to obtain a firing bearing with her main guns. Four high-angle twin mounts would turn every Tribal into a valuable fleet air-defense destroyer and remove the historical need to replace one 4.7-inch mounting with a 4-inch high-angle mount. An 80-degree maximum elevation is slightly below the 4-inch weapon's 85 degrees, but still sufficient for the intended defensive role.
Chapter · 37:11-41:42
Narvik and Gurkha show the tactical value of high elevation
The 4.5-inch gun changes little in the surface battle at Narvik but allows Tribal destroyers to defend themselves and their formations against aircraft.