The aircraft which could have been the first to break the speed of sound. Why was it cancelled? I have heard that decision to cancel it was based on the assumption that a straight-wing aircraft would not be capable of breaking the speed of sound, the Bell X-1 was straight-wing though. Another reason given was the fear that an attempt at the speed of sound simply was too dangerous.
And presumably cost. I do not know exactly why it was cancelled. I do know that the Bell X-1 looked pretty similar, and IIRC employed the all-moving rear wings that Miles developed to provide controllability at high speed. here has a good write up, and blames the cancellation on the new Labour government deciding that it was simply a waste of money.
