The car was a Rolls-Royce Silver Cloud III, with a coachbuilt convertible body by Mulliner Park Ward, designed by Vilhelm Koren. It is informally known as the "Chinese Eye" due to its slanted headlights. It has the same chassis as the Silver Cloud III, but it looked very different due to its coachbuilt bodystyle. About a hundred cars were built in coupe and convertible form 1962 to 1966. The car used in the film belonged to 60s media personality and was originally white but was painted black for the film. You can read more about that particular model here or here.