It was cutting edge and in a way the Franco-British Apollo program in terms of engineering. I mean not only in terms of speed, but engines, material, fly by wire, anti skid (aka abs), carbon brakes, CoG adjustment to reduce drag, even the now common Airbus flight stick was tested on Concorde...

I remember reading a book by an engineer from the Concorde program (he's from the UK) who got invited by the Americans working on the B-1 bomber (which was initially supposed to be a M2.2 thing).

They wanted to exchange about air intakes problems such as efficiency, surges, and all. The author was not impressed at all by what had been developed and tested on the B-1. And he thought what they had on Concorde was so much more advanced (he might have been totally biased of course).

Because as people say, Concorde was not tested, it was developed (hence the many prototypes, pre-production and first production models) because a lot of the technology had to be created and if it didn't, it had to be modified to be usable on a civilian aircraft.

A classic example is pulling the throttle all the way back while at full speed: on most fighter jets of the era, you'd completely trash the turbine if you did that. So they had to create a plane which did the right thing for pilots who weren't trained like fighter pilots...

It was also a case of doing all the wrong thing in terms of management. Like assembling two of the same things on each side of the Channel to please respective governments...