Distance and a telephoto lens can fix a lot of that. If you're kilometers away going twice as fast you have a lot more time to snap a pic, versus being 500 meters away.
They used these for surveillance so I assume the motion compensation on these things was state-secret levels of good.
It's just that the performance tables in the manual (which has been released to the public) only go down to mach 2.2, so you are outside of the certified/documented regimen.
Concorde development was a (UK & France) national project. They would have had easy access to military aircraft. Aircraft like the Lightning might only just have been able to intercept but would easily have observed pre-arranged tests.
It's almost inconceivable that the test flights would not have been closely recorded, especially the significant ones including trans-sonic and supersonic ops. Despite the best design and air-tunnel work, you'd expect that things would go wrong and you really want to learn as much as possible from any incidents/events.
Unfortunately, all this happened well before the internet age, and so records and images are not so easily found :(
Only publicity photo, surely.