Did anybody really believe the idea that GB and France intended to build a supersonic airliner ? with hindsight it should have been obvious that the economics didn't work after all only one has ever entered (limited) service (TU144 with only 55 scheduled flights and that was rumoured to have be 'helped' to start by the Anglo-French deception plan).
But the Concorde project did manage to hide a very powerful Anglo-French aircraft the Aérospatiale-BAC SSR4.....