It is the Nostalgia forum I know, but Bill Waterton convinced me that a tp should always tell the truth regardless.
I always thought they were right to cancel these four as I believed they had fundemental flaws:
TSR2 Not enough wing
P1154 Exhaust gas pressures and temps too high to allow
any operating site flexibility (which iswhat VSTOL has
to be all about)
AW681 Helicopters would do the tactical support job more
cheaply and reliably
Rotordyne The noise of a tip jet driven rotor was never going
be acceptable in city centres
Mind you I realise they were not cancelled for these reasons