Can Astute-class submarines cover UK home defence?

Could the Astute class serve as the United Kingdom's main home-defence force?

For the fleet described in May 2022, not by itself: the class was too small once boats were allocated to High North intelligence work, the South Atlantic, the Far East, and other commitments.

Availability, rather than headline capability, is the decisive issue. An Astute-class submarine committed to intelligence gathering or an overseas station cannot simultaneously defend home waters. Earlier policy assumptions were formed when the Royal Navy also operated double-digit SSK and SSN fleets and the Royal Air Force maintained many more air-defence fighter squadrons. Reusing those assumptions after the supporting force structure has disappeared creates a defence plan without enough platforms to execute it.