According to John Heseltine (who restored the car for the film) David Niven couldn't master the idiosyncratic gearbox of the Cord 810 and subsequently it was driven in bottom gear, resulting in it overheating. The scene in the film showing the steaming Cord was hastily rewritten to work around the problem. The car had to be restored from nothing but a rusty collection of parts in just six months to get it ready for filming.