Colette Bartrop plays the mistress of Anton Diffring's character. According to the credits, the character's name is Penny, but Diffring calls her "Colette" throughout the film.
The hero flies New York to London in a DC-3. That plane would not be able to do that in one single flight. It would have to go, New York, Canada, Greenland, Iceland Scotland and London. It would take a minimum of 48 hours. He arrives in the same suit, wrinkle-free. A commercial flight would have taken 18hrs.