Clearly Tim, a total force of around a dozen interceptors (sufficient to intercept any 9-11 wannabee) would be sufficient to defend UK airspace then? If we're not off "crusading" as you put it, we don't need AT or SH either. The interceptors wouldn't even have to be hi-performance (ie dogfighters or low observables), because there are no "direct" air threats to our borders anymore.......
See how easy it is once you get going.......