Just a wild guess here but was it a Sir John Black proposal/prototype for the Triumph 1800/Renown?
It is indeed a development of the 1800, which eventually resulted in the razor-edged Renown.
As to who designed it, I'm not sure but I'll look further into it to see if I can find that out.
So you're getting a point but I'll have a look into it first before I give you it and move it!