I actually thought it was a saloon built for record attempts, and was searching for Bentleys or something similar.
The car was a 1934 model to Works Specification, which Dr Roth had converted in 1935 to single-seat form, and with a body resembling the current Mercedes-Benz W25. Presumably this photo was taken at that time - I can't imagine any venue being suitable in 1942.
I think that must be a very high headrest which makes it looked like an enclosed cockpit.