If the RAF is so convinced that the UK is never going to get into a shooting match without US Top cover... Why are they buying Typhoon?
a. Because we signed the multi-national contract years ago and the other countries would make us pay even if we cancelled. Same deal as the Germans found over the A400M. We can always try and flog some of the product slots to the RSAF as part of an update to the Al Yamamah contract.
b. Keeps lots of lovely jobs in factories in MPs constituencies building aircraft. Not many jobs involved in just keeping an old aircraft flying.
c. Hopes of overseas orders (triumph of hope over experience).
d. Retention of aircraft design and construction expertise (same reason they built the EAP before the Eurofighter came along).