Trident missiles based in subs are able to reach anywhere in the world, no matter how far inland, and cannot realistically be stopped. Cruise missiles have a more limited range and travel at subsonic speeds and could potentially be shot down before reaching their target. Britain’s nuclear deterrent would therefore be diminished.
Sub-based ballistic missiles are the only game in town when it comes to a reliable strategic nuclear deterrence...
Well my point was only about cost-cutting!!! The UK really has little practical choice in this matter. Cutting Trident would mean a diminished strategic capability but it would in theory at least give greater latitude to conventional weapons capability.