Bucklers!

[Oldfart]

I think the timing is approximately correct for the beginnings of the de Joux bodies, the first dated one I have a record completed is 1957. It's possible the person you are thinking of is Bruce Sutcliffe. It was quite common for de Joux bodies to use the rear screen of a Humber 80, that may be what you have.That hard top looks very much like Healey.
I have no photographic evidence to show any raced with a hard top, doesn't mean they weren't though, and of course if was a road car, which the cast head and such may suggest possible, then finding evidence if it's needed may be a bit difficult.