During filming, 19-year-old Hayley Mills started a relationship with Roy Boulting, the film's 52-year-old director. The affair made jaws drop, not only because of the couple's 33-year age difference, but also because Boulting was married with children. Mills, however, didn't see their age difference as an issue at the time. "The fact that he was considerably older was probably part of the attraction, but not consciously," she later recalled for her biography on A&E. "And having spent an awful lot of time with people much older than myself on film sets, etc., it didn't seem particularly odd or peculiar to me." Despite all the controversy, Mills and Boulting were married from 1971 to 1977 and had a son in 1973. However, by the mid-1970s the age difference had become a major issue for 29-year-old Hayley and her 62-year-old husband, leading to separation and eventual divorce in 1977.
Howard Sounes' biography of Sir Paul McCartney credits George Martin with doing most of the composing.
According to Steven C. Smith's biography of Bernard Herrmann, he was asked to advise Sir Paul McCartney on how to score his first movie. Instead of a fee, the Boulting Brothers gave Herrmann a Marc Chagall painting.
Marjorie Rhodes was nearly 70 years old when she played the mother of Hywel Bennett and Murray Head, whose characters were meant to be in their late teens or very early twenties; in real life, Bennett was 22 and Head was 20.