My grandfather had a Jaguar XK150 S drophead coupe, mist grey with carmine red wire wheels and registration "S 150". He owned it from new in 1959 until 1976, and as a small boy I used to ride in it regularly, sometimes in the back (with a WW2 leather flying helmet and goggles, which were a blessing at high speeds!). He was a bit of a nutter and took the 'racing line' round all bends, regardless of whether he could see if anything was coming the other way! Jaguar's motor racing PR guy was a personal friend of his, and the car was reputed to have had a 'tweaked' motor fitted at the factory. It was kept in concours condition and went to the Heritage Motor Collection at Gaydon - it's come up for sale a few times since then, still in pretty original condition. I found these pictures on the web: