The ORIGINAL design for the reheat was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls-Royce baled them out, and it became a Rolls-Royce/ SNECMA design.
ref heritageconcorde.com
Does anyone have any details on the 'joint' development alluded to above?
Attended a Powerplant Design Group reunion earlier, so I thought I would try to get an answer from somebody who really knows ....
The problem apparently was that flame stabilisation operating in "contingency" rating was sensitive to the point that every engine had to be checked, so there was a lot of engine plus reheat testing, most of which was done at Patchway. The solution was addition of some form of 'spike' at various points on the spray bar (my informant wasn't very specific). It sounded like a sort of vortex generator cum chine that gave the flame somewhere to latch onto. The development process was, as you suggested, a joint activity.