Yup, those modifications were fantastic, quality engineering! The clutch control lever on the gearstick and linked to the clutch pedal was particularly nice. All that trouble to design and make it, yet it seems that he himself never actually drove it, just wanted to be able to if the need arose! The rich get what they want!
I particularly liked the airstreamed car in black over old English white.
I had the impression that RR had always been very particular about what it did with its cars, even in those days when independent coach-builders did all the bodywork, but they were amazingly open to unusual requests and specifications.