Miranda Richardson and Kristin Scott Thomas were both considered for the role of Sarah Miles, before Julianne Moore personally wrote a letter to director Neil Jordan, asking for the part in the film. Her method worked, and she was offered the role.
The film that Maurice and Sarah see is 21 Days Together (1940). Graham Greene, the author of novel on which this movie is based, co-wrote the script for 21 Days, although the name of the film they see in the novel is never mentioned.
Neil Jordan wanted his longtime collaborator, composer Elliot Goldenthal to do the film, but Goldenthal was committed to score Titus (1999) for his companion, Julie Taymor. John Barry was considered, and he wrote a demo theme for the film, which ended up on his 2001 solo album "Eternal Echoes," but Jordan eventually settled on Michael Nyman.
Surprisingly, this genteel period drama was granted an 18 certificate in the UK (the equivalent of an NC-17 rating). This was mainly down to the fact the censor found Ralph Fiennes' gyrating buttocks in the numerous sex scenes to be too graphic.
Ralph Fiennes plays a similar character in The English Patient (1996), in which he carries on a doomed relationship with a married woman.