Battleships became unnecessary once the anticipated fleet battle disappeared; their guns and armour did not cease to work. The Royal Navy expected its existing carriers to adapt to the jet age, but learned too late that they could not. The cancelled Malta class and the larger Audacious designs offered more room for adaptation than the fleet carriers Britain retained. Vanguard consequently survived as insurance while the navy tested technologies for future destroyers and cruisers.
Chapter · 7:09-8:42
Unnecessary is not the same as obsolete
The Royal Navy kept Vanguard as an insurance policy while expecting carriers and new destroyer technology to meet future needs.