A better option (to my mind) would be Submarine-Launched, Nuclear-Tipped, Cruise Missiles.... can be deployed from 'conventional' subs (not needing a 'dedicated' vessel) - effectively making EVERY British submarine a deterrent (in that it wouldnt be known to a potential agressor whether a given vessel had the nuclear Cruise aboard) thats if we really do still need one - which is a matter for further debate anyhow.