Time scales and politics
A week is a long time in politics...
By the time these ships are built HM the Queen may no longer be with us (hopefully not) Scotland could be independent and the bill dumped on Westminster for the divorce so crippling that anything might get the chop.
The decision to axe the Harrier was not in my opinion a good one containing an element of anger and spite caused by the new coalition government getting the true picture of MODs black hole.
Something for which they, the Labour politicians, senior civil servants and Chiefs of Staff etc were never punished for while those left to serve were left to muddle on with little money and unexpected demands like Libya.
The only up side is that in a period of political upheaval akin to the 1930s we may need to keep both ships. Let's not forget Hitler was elected in 1933, we were at war six years later and six years after that Europe in bits and on its way to a cold war that lasted 50 years...