Why the Royal Navy delayed adopting the Mark 45 five-inch gun

Why did the Royal Navy not adopt the BAE-owned Mark 45 five-inch gun earlier?

Its existing 4.5-inch logistics made continuity cheaper until the Type 26 created a natural point for change.

The Mark 45 is a capable weapon and has potential value against drones, but corporate ownership by BAE did not make it an automatic British choice. The Royal Navy already had a long investment in 4.5-inch guns, ammunition, training, and support. Staying with that system reduced disruption until a new ship class justified the transition. The Type 26 therefore becomes the point at which Britain adopts both the five-inch Mark 45 and other US-origin launch-system standards. The answer is a practical example of installed logistics outweighing a simple comparison of weapon performance.