Anthony Hopkins had previously portrayed C.S. Lewis in Shadowlands (1993) 30 years prior to this film.
The waltz, called "And the Waltz Goes On" that is played right before the end cards was composed by Anthony Hopkins.
Both Anthony Hopkins and Matthew Goode were at the time of this film's release only a few years older than the characters they were playing Sigmund Freud and C.S. Lewis, Hopkins being 85 to Freud's 83, and Goode being 45 to Lewis' 40.
By contrast, the actresses Orla Brady and Liv Lisa Fries are both considerably younger than the characters they play, Janie Moore and Anna Freud, Bradie being 62 to Janie Moore's 77 and Fries being 33 to Anna Freud's 44.
Somewhat late in this film, Lewis says to Freud (played in this film by Anthony Hopkins) "What if God wants to perfect us through suffering? Make us realize that real happiness, eternal happiness, can only come through him? If pleasure is his whisper, pain is his megaphone." In the 1993 film Shadowlands (1993) in which actor Hopkiins plays C.S. Lewis, quite early in the film, Lewis says in a radio broadcast " I suggest to you that it is because God loves us that He makes us the gift of suffering. To put it another way, pain is God's megaphone to rouse a deaf world."
The closing credits have multiple title cards explaining things that happened to both Lewis and Freud after the events of this film. They mention that during World War II, Lewis housed children being evacuated from London during the Nazi air raids. They do not mention that one of these was Jill Flewett, who later married a grandson of Sigmund Freud, Clement Freud.