Just to add whatever information I managed to obtain, this car was entered in a Formula 3 race in August 1964 at Silverstone, but did not arrive. The driver was nominated as Robert Cowey, and the entrant was Erik Johnson. That's all the internet will reveal.
In the puzzle photo, it's fitted with mudguards. This makes me think that it was a sort of 2-seater, which could enter sports car events and then be stripped down for F3 races. Just like the 1950 HWM!