Caterham makes a track car, and Radical converts a track car to a street legal road car. Nice, but Radical really should put in a bit more engineering and put in a roof. While they're at it, they should remove the front splitter.
What they'll get is a mini Le Mans street legal racer. And it'll sell. To fit a roof, they'll have to figure out how to build doors into the chassis (or maybe some innovative folding roof mechanism).