Lease Russian subs (just like India) diesel and nuclear. Much cheaper and quicker. Then you can upgrade every few years. Just for other point of view - we are unlikely ever to go to war with Russia. Have a look at fortification built in Sydney in 1850, Catch cry of the day was same as today - Russians are coming. They never came and fortifications were never used in anger. Leased Russian subs will be very effective denying our neighbours free passage to our shores for living space in very near future not in a decade or so.
