CliveL, correct me where I'm wrong.
* Most deltas develop some vortex lift, and there were several deltas flying long before Concorde, so the phenomenon was not unknown.
Shaping the wing, and in particular the leading edge, optimised the effect on Concorde.
* The ogee (slender delta) wing was original proposed by NASA (possibly still NACA at the time) as best suited for a supersonic transport. The information was in the public domain by the time the "BAC223" and "Super Caravelle" were first revealed (they later "merged" into the Concorde design).
The Tu-144 design used the same information, which is a major reason for its resemblance to Concorde, rather than espionage...
How much the full advantages of the 'vortex lift' were understood at the time, is still an open question, IIRC.
I'll have to look for the original NASA TN (Tech Note)... it may be on the web somewhere.
* I would think the Handley Page HP115 slender-delta low-speed test aircraft must have contributed some details about vortex lift.
Sorry, I can't find my own photos of the beast.
It's now in the Fleet Air Arm Museum at Yeovilton (UK), together with Concorde 002 and the BAC-221.
It still has the "smoke tube" on the left wing leading edge, that was used to visualise the vortex over the wing (not yet fitted when the photo above was taken).
CJ