"Never Let Me Go" is Carey Mulligan's favorite novel. She was certain someone would make a film adaptation, and had hoped they could wait until she was old enough to play Kathy. She couldn't bear the idea of anyone else portraying Kathy, although she acknowledged that she thought other people would be able to do a better performance. She actively campaigned for the role of Kathy.
Mark Romanek said that working with child actors was the most challenging part of making the film, since "the first act of the film was going to have to be carried by 12-year-olds." At rehearsals, Romanek had the younger actors watch the older actors practice their scenes so the older actors would have a memory of having played those scenes, while the child actors would get a better idea of how a more skilled actor would play their part. He also had the child actors spend time together playing and talking to create chemistry between them. He took them to the school set and let them play there so they could get a better idea of the layout.
Carey Mulligan had to learn how to drive for the film. She took a two-week intensive course, but failed the driving test. Her scene was shot on a private road, where she was allowed to get behind the wheel.
Keira Knightley admitted that she only agreed to appear in the film because her friend and co-star Carey Mulligan had asked her to. She said she was unable to relate to Ruth's involvement in a love triangle.
Mark Romanek found making Keira Knightley look plain almost impossible. He told an interviewer "It was difficult. She was eager and happy to do it because the role called for it. But even at her worst, Keira still looks astonishing".
Composer Rachel Portman described her score as a "chamber piece." She worked with an orchestra of 48 players, including piano, strings, and harp, plus a violin and cello for solos. She felt that a smaller orchestra was needed for a minimal, more restrained intimate score. Because of the film's sad story she wanted the music to have some hope, humanity, and heartbeat.
Mark Romanek was glad to get the opportunity to direct this film "From the moment I finished the novel, it became my dream to film it. Kazuo Ishiguro's conception is so daring, so eerie and beautiful."
The trivia items below may give away important plot points.
A subplot that was excised from the film was that the clones were genetically modified so that they would be sterile. This provides an explanation for the title of Kathy's favorite song. The children were raised in full knowledge of what would follow. A brief life with no chance of ever having children. When young Kathy hugs the pillow and listens to the song "Never Let Me Go" the novel clarifies that the pillow stands for an imaginary baby.
Although the deferrals were simply rumors stemming from the hopelessness of the orphans, the students of Hailsham were indeed special. The climactic scene with Tommy and Kathy visiting Madame was truncated in the film . In the novel Miss Emily elaborates on the life in Hailsham by explaining that she took special care that the children were raised properly and happily. In other similar institutes the children lived under harsh conditions and many of their basic needs were not covered. She even hints at possible abuse by the staff . It was the lack of a nice treatment that prompted the rumors among the inmates from other boarding schools that the Hailsham alumni may have better chances in life (as it is clearly shown in the Norfolk scenes) . Miss Emily also explains that she did everything in her power to stop those rumors but just like weed they continued to spread among the orphans.
Alex Garland's final shooting script retains the "Never Let Me Go" song scene as it was written in the novel. It is Madame and not Ruth the one observing young Kathy singing while listening to the tape. Madame was so moved by the emotional intensity of the scene that she shed tears. Many years later they are reunited and Madame explains to Kathy why she was affected sentimentally by this incident. During production the scene was altered and Ruth witnesses Kathy hugging the pillow. In the novel Kathy spends many years thinking that Madame misunderstood the song and she regarded the pillow as a symbol of an imaginary lover. Interestingly, this is precisely what happens in the film judging from the bitter look on Ruth's face. This fuels the rivalry for Tommy later on when the children become adolescents and leads more fluently to the scene where Ruth, Tommy and Kathy go on a field trip to the area with the stranded boat.