From the obituary of Adrienne Corri, who died this month at the age of 84.
I went looking for more information about Corri's experience. I found this:
Adrienne Corri initially declined the role of Mrs. Alexander because Kubrick was getting applicants to de-bra in his office while he trained a video camera on them. She made it clear that wasn’t on. “But Adrienne, suppose we don’t like the tits?” “Tough.”And:
Little was accomplished during the first two days of shooting [the rape scene with Corri], but on the third day, Kubrick blocked out a portion of the action with McDowell, instructing him to knock [the actor Patrick] Magee to the floor and begin kicking his guts out. The director then suddenly asked McDowell, "Can you sing?" It was suggested that the actor could improvise a song-and-dance number while administering the savage beating. McDowell confessed that "Singin’ in the Rain" was the only tune he knew by heart. This resulted in what Kubrick calls the CRM, or "critical rehearsal moment," during which the director and actors come together to create a defining scene. Kubrick immediately looked into obtaining the rights to the song, and discovered that the fee was $10,000 to use it for 30 seconds. Once the rights were in hand, shooting proceeded immediately. Kubrick later invited Stanley Donen, the director of the musical classic, to view his scene and then asked Donen’s personal permission to use the song for the sequence. "He wanted to make sure I wasn’t offended," Donen reports in the biography Dancing on the Ceiling. "Why would I be? It didn’t affect the movie Singin’ in the Rain." Gene Kelly, who had performed the famous number in the 1952 film, felt otherwise. When Kelly and Kubrick met at an awards ceremony following Clockwork’s release, the danceman refused to talk to the director.