Why Britain moved from V-bombers to submarine deterrence

Why did Britain not rely on a land-based nuclear missile force?

Suitable secure, flat, well-connected sites were limited and expensive, so Britain used V-bombers before shifting the strategic deterrent to submarines.

Land-based launch facilities required suitable ground in secure locations. The sites also needed enough flat land and supporting infrastructure for construction. Those requirements sharply limited the available choices within the government's budget. Britain consequently used V-bombers first and later moved its strategic deterrent to submarines.