As a Chartered Engineer working on a multi-disciplinary rail project, I am amazed that a project as complex as this was managed across the Channel in the 1960's; how was the Systems Engineering managed - who drove the requirements for the Jet, potential carriers, engineers or politicians?
For sure not the politicians, who could not distinguish between their rectum and middle arm joint so far as aircraft systems were concerned
Once it was decided to go, I would say that the system requirements were largely driven by the difficulty of the task - more a question of finding out how to make it work than of optimising. The overall aircraft requirements were driven by the engineers, but criticised by the potential customer airlines in regular meetings.
Safety requirements were specified in a completely new airworthiness code - a sort of comprehensive set of special conditions, which were generally more severe than the subsonic codes of the time. Concorde, for example, was,
AFAIK, the first civil aircraft to be certificated against the requirements that now exist as 25.1309.
But nobody really knew what to write for supersonic flight and, in particular, the transition from subsonic, so to some extent one made it up as one went along, using prudent common sense and engineering judgement. Fuel system transfer rates for example had to match a requirement that it should be possible to abandon the acceleration at any point and return safely to subsonic conditions - and the deceleration was much quicker than the acceleration!
wind modelling played a big part in the development of the aerodynamics, how big did the models go? Did you have the luxury of testing a full-scale model? or maybe full-scale parts or sub assemblies?
Well some people might say we had four full scale models - two prototypes and two pre-production models
Supersonic testing mainly at 1/30 scale; low speed 1/18. The biggest model was a 1/6 scale half model used mainly for icing tests. Isolated intake tests, IIRC, about 1/10 scale, but we did have a full scale intake operating in front of an Olympus 593 at Mach 2.0 in Cell 4 at NGTE Pyestock.