It's "The Monster". Starting out life as a 1920s Crossley 20/70 tourer, owned by John & Vida Jones, it was sold to Bob Pritchett in 1938, who fitted it with a supercharged Mercedes engine and modified it to mimic a contemporary Mercedes. Quite a beast, and a neat piece of work. You're right, this car has been all over the net for quite a while, again surprised no rookies appear to have known of it.