Well
AFAIK, the basic delta concept was devised by Lippisch in Germany, and developed there during WWII.
It would be true to say that Chadwick was one of the first outside Germany to use it, but that was essentially with a rounded leading edge, which is a very different animal from the slender delta with a sharp leading edges to deliberately produce strong vortices which give non-linear lift at high AoA.
That concept was definitely the brainchild of Kuchemann and his team (mostly fellow Germans
) at RAE Farnborough.