“That cleared up, it’s on to Jung. “I think he was far more forward thinking than Freud, far more fluid,” says Fassbender. “Freud, I think, brought a lot of his own neuroses into other people’s lives. Jung was very modern in his thinking, and he didn’t have any set ideas.

“Freud was staid, whereas Jung explored astrology and dealt with the spiritual world and was more interested in theology. To Freud, this was hocus-pocus, sure to bring their work into disrepute. But with Jung, nothing was closed off and no areas deemed ridiculous.”

Initially great friends who traded academic letters and ideas with a boyish enthusiasm, Freud and Jung diverged – intellectually, ideologically, emotionally – with the arrival of Sabina. It’s this parting of ways that Oscar-winning scribe Christopher Hampton’s screenplay (based on his own stage play A Talking Cure, which itself began life as an unoptioned screenplay) traces.