The car started out as a private venture in 1966 by company engineer Erich Waxenberger. His principle was simple: take the powerful 6.3 litre Mercedes-Benz M100 V8 from the massive 600 saloon and limousine, and fit it into the engine bay of the top-end 6-cylinder 300 SEL W109 model. The result was pavement-ripping muscle car performance. It is said that chief Mercedes engineer Rudolf Uhlenhaut, when invited to test drive the prototype, opened the hood at the first red light to find out how the big engine and its supporting equipment had been squeezed in there.