At one point in time, Mercedes-Benz built, arguably, the finest luxury automobiles in the world.

In its post-war recovery, they shifted focus towards more practical family saloons, followed by cars of a more sporting nature.

By the early 1960s, however, Rudolf Uhlenhaut felt the time had come for Mercedes-Benz to re-establish itself as a builder of ultra-premium models, ones where, in his words, “costs were of secondary importance.” As impressive as the rest of the car was, however, its biggest break from convention was the hydraulic system that operated the windows, power seats, sunroof, doors, boot, suspension damping and ventilation system.

While lesser vehicles used electric motors to regulate many of these functions, the Mercedes-Benz engineers believed that if cost was no object, hydraulic systems, would be smoother, quieter and longer-lasting.

The complicated nature and limited numbers built have now meant that examples of the 600 series are relatively rare and usually enorm...