Since the demise of the F111 we have lacked strategic strike. Among many other functions, the new subs would remedy that by being equipped with land attack cruise missiles. They would have a range and capability far beyond the ageing and almost completely useless Collins class boats they would replace.
Subs with cruise missile capability are not a "remedy" for the F-111 strike capability (given away by Defence on a lie).
The F-111 could reach out with stand-off weapons and hit a target within hours; not days. Fly home. Rinse and repeat.
Subs with cruise missiles are unable to do such a thing. Ever. While the capability may be useful, it isn't a "remedy" for long-range strike capability delivered by aircraft.
