- Alfonso Cuarón – director, screenwriter, editor
- Timothy J. Sexton – screenwriter
- David Arata – screenwriter
- Mark Fergus – screenwriter
- Hawk Ostby – screenwriter
- Hilary Shor – producer
- Iain Smith – producer
- Tony Smith – producer
- Marc Abraham – producer
- Eric Newman – producer
- Emmanuel Lubezki – cinematographer
- Jim Clay – production designer
- Geoffrey Kirkland – production designer
- Álex Rodríguez – editor
- Jany Temime – costume designer
- John Tavener – composer
The adaptation of the P. D. James novel was originally written by Paul Chart, and later rewritten by Mark Fergus and Hawk Ostby. The studio brought director Alfonso Cuarón on board in 2001. Cuarón and screenwriter Timothy J. Sexton began rewriting the script after the director completed Y tu mamá también. Afraid he would "start second guessing things", Cuarón chose not to read P. D. James' novel, opting to have Sexton read the book while Cuarón himself read an abridged version. Cuarón did not immediately begin production, instead directing Harry Potter and the Prisoner of Azkaban. During this period, David Arata rewrote the screenplay and after some back and forth with the director (Cuarón said that Arata "was trying to turn this into a generic action movie"), delivered the draft which secured Clive Owen and sent the film into pre-production. The director's work experience in the United Kingdom exposed him to the "social dynamics of the British psyche", giving him insight into the depiction of "British reality". Cuarón used the film The Battle of Algiers as a model for social reconstruction in preparation for production, presenting the film to Clive Owen as an example of his vision for Children of Men. In order to create a philosophical and social framework for the film, the director read literature by Slavoj Žižek, as well as similar works. The film Sunrise was also influential.
A Clockwork Orange helped contribute to the futuristic, yet battered patina of 2027 London. Children of Men was the second film Cuarón made in London, with the director portraying the city as a character itself, shooting single, wide shots of the city. While Cuarón was preparing the film, the London bombings occurred, but the director never considered moving the production. "It would have been impossible to shoot anywhere but London, because of the very obvious way the locations were incorporated into the film," Cuarón told Variety. "For example, the shot of Fleet Street looking towards St. Paul's would have been impossible to shoot anywhere else." Due to these circumstances, the opening terrorist attack scene on Fleet Street was shot a month and a half after the London bombing.
Cuarón chose to shoot some scenes in East London, a location he considered "a place without glamour". The set locations were dressed to make them appear even more run-down; Cuarón says he told the crew "'Let's make it more Mexican'. In other words, we'd look at a location and then say: yes, but in Mexico there would be this and this. It was about making the place look run-down. It was about poverty." He also made use of London's most popular sites, shooting in locations like Trafalgar Square and Battersea Power Station. The power station scene (whose conversion into an art archive is a reference to the Tate Modern), has been compared to Antonioni's Red Desert. Cuarón added a pig balloon to the scene as homage to Pink Floyd's Animals. Other art works visible in this scene include Michelangelo's David, Picasso's Guernica, and Banksy's British Cops Kissing. London visual effects companies Double Negative and Framestore worked directly with Cuarón from script to post production, developing effects and creating "environments and shots that wouldn't otherwise be possible".
The Historic Dockyard in Chatham was used to film the scene in the empty activist safehouse.
Style and design
"In most sci-fi epics, special effects substitute for story. Here they seamlessly advance it," observes Colin Covert of Star Tribune. Billboards were designed to balance a contemporary and futuristic appearance as well as easily visualizing what else was occurring in the rest of the world at the time, and cars were made to resemble modern ones at first glance, although a closer look made them seem unfamiliar. Cuarón informed the art department that the film was the "anti-Blade Runner", rejecting technologically advanced proposals and downplaying the science fiction elements of the 2027 setting. The director focused on images reflecting the contemporary period. 
Children of Men used several lengthy single-shot sequences in which extremely complex actions take place. The longest of these are a shot in which Kee gives birth (199 seconds; 3:19); an ambush on a country road (247 seconds; 4:07); and a scene in which Theo is captured by the Fishes, escapes, and runs down a street and through a building in the middle of a raging battle (378 seconds; 6:18). These sequences were extremely difficult to film, although the effect of continuity is sometimes an illusion, aided by CGI effects.
Cuarón had experimented with long takes in Great Expectations, Y tu mamá también, and Harry Potter and the Prisoner of Azkaban. His style is influenced by the Swiss film Jonah Who Will Be 25 in the Year 2000, a favorite of Cuarón's. Cuarón reminisces: "I was studying cinema when I first saw [Jonah], and interested in the French New Wave. Jonah was so unflashy compared to those films. The camera keeps a certain distance and there are relatively few close-ups. It's elegant and flowing, constantly tracking, but very slowly and not calling attention to itself."
The creation of the single-shot sequences was a challenging, time-consuming process that sparked concerns from the studio. It took fourteen days to prepare for the single shot in which Clive Owen's character searches a building under attack, and five hours for every time they wanted to reshoot it. In the middle of one shot, blood splattered onto the lens, and cinematographer Emmanuel Lubezki convinced the director to leave it in. According to Owen, "Right in the thick of it are me and the camera operator because we're doing this very complicated, very specific dance which, when we come to shoot, we have to make feel completely random."
Cuarón's initial idea for maintaining continuity during the roadside ambush scene was dismissed by production experts as an "impossible shot to do". Fresh from the visual effects-laden Harry Potter and the Prisoner of Azkaban, Cuarón suggested using computer-generated imagery to film the scene. Lubezki refused to allow it, reminding the director that they had intended to make a film akin to a "raw documentary". Instead, a special camera rig invented by Gary Thieltges of Doggicam Systems was employed, allowing Cuarón to develop the scene as one extended shot. A vehicle was modified to enable seats to tilt and lower actors out of the way of the camera, and the windshield was designed to tilt out of the way to allow camera movement in and out through the front windscreen. A crew of four, including the director of photography and camera operator, rode on the roof.
However, the commonly reported statement that the action scenes are continuous shots is not entirely true. Visual effects supervisor Frazer Churchill explains that the effects team had to "combine several takes to create impossibly long shots", where their job was to "create the illusion of a continuous camera move." Once the team was able to create a "seamless blend", they would move on to the next shot. These techniques were important for three continuous shots: the coffee shop explosion in the opening shot, the car ambush, and the battlefield scene. The coffee shop scene was composed of "two different takes shot over two consecutive days"; the car ambush was shot in "six sections and at four different locations over one week and required five seamless digital transitions"; and the battlefield scene "was captured in five separate takes over two locations". Churchill and the Double Negative team created over 160 of these types of effects for the film. In an interview with Variety, Cuarón acknowledged this nature of the "single-shot" action sequences: "Maybe I'm spilling a big secret, but sometimes it's more than what it looks like. The important thing is how you blend everything and how you keep the perception of a fluid choreography through all of these different pieces."
Tim Webber of VFX house Framestore CFC was responsible for the three-and-a-half minute single take of Kee giving birth, helping to choreograph and create the CG effects of the childbirth. Cuarón had originally intended to use an animatronic baby as Kee's child with the exception of the childbirth scene. In the end, two takes were shot, with the second take concealing Clare-Hope Ashitey's legs, replacing them with prosthetic legs. Cuarón was pleased with the results of the effect, and returned to previous shots of the baby in animatronic form, replacing them with Framestore's computer-generated baby.
Cuarón uses sound and music to bring the fictional world of social unrest and infertility to life. A creative yet restrained combination of rock, pop, electronic music, hip-hop and classical music replaces the typical film score. The mundane sounds of traffic, barking dogs, and advertisements follow the character of Theo through London, East Sussex and Kent, producing what Los Angeles Times writer Kevin Crust calls an "urban audio rumble". For Crust, the music comments indirectly on the barren world of Children of Men: Deep Purple's version of "Hush" blaring from Jasper's car radio becomes a "sly lullaby for a world without babies" while King Crimson's "The Court of the Crimson King" make a similar allusion with their lyrics, "three lullabies in an ancient tongue".
Amongst a genre-spanning selection of electronic music, a remix of Aphex Twin's "Omgyjya Switch 7", which includes the 'Male This Loud Scream' audio sample by Thanvannispen, not present on the original (nor indeed on the official soundtrack) can be heard during the scene in Jasper's house, where Jasper's "Strawberry Cough" (a potent, strawberry-flavoured blend of marijuana) is being sampled. During a conversation between the two men, Radiohead's "Life in a Glasshouse" plays in the background.
A number of dubstep tracks, most notably Anti-War Dub by Digital Mystikz, as well as tracks by Kode9 & The Space Ape and Pressure are also featured.
For the Bexhill scenes during the film's second half, the director makes use of silence and cacophonous sound effects such as the firing of automatic weapons and loudspeakers directing the movement of "fugees" (illegal immigrants). Here, classical music by George Frideric Handel, Gustav Mahler, and Krzysztof Penderecki's "Threnody to the Victims of Hiroshima" complements the chaos of the refugee camp. Throughout the film, John Tavener's Fragments of a Prayer is used as a spiritual motif to explain and interpret the story without the use of narrative.
A few times during the film, a loud, ringing tone evocative of tinnitus is heard. This sound generally coincides with the death of a major character (Julian, Jasper) and is referred to by Julian herself, who describes the tones as the last time you'll ever hear that frequency. In this way, then, the loss of the tones is symbolic of the loss of the characters.