Keira Knightley every inch the star at Venice Film Festival

Ms Knightley plays a psychiatric patient-turned-analyst in the film, a period drama that examines the relationship between the two founders of modern psychoanalysis, Sigmund Freud and Carl Jung.

At a packed press conference, director David Cronenberg motioned to Viggo Mortensen, who plays Freud, and Michael Fassbender, who plays his protégé Jung, and joked: “I think my cast has great need of psychoanalysis, which is why I cast them actually, to introduce them gently to the idea that they needed help, a lot of help.

“You can see they are much better people. Before they were messes. When I found them, they were neurotics, hopeless.”

The movie focuses on Freud’s relationship with Jung, from their mutual enthusiasm at finding kindred spirits in the development of new methods of treating psychiatric patients, then building up to their ultimate split over differences over Freud’s adherence to theories about sex and Jung’s interest in mysticism as a path to self-realisation.

While their professional differences were couched in mostly clinical terms, a clear catalyst for their alienation was Ms Knightley’s character, Ms Spielrein, whose recovery from hysteria under Jung’s treatment validates Freud’s sexual theories. The mentor-protege relationship goes awry when Jung gives in to Ms Spielrein’s sexual advances.