Go here to find a short article from DV Guru about the editing in Children of Men. Here is a snippet:
The complete lack of editing during some of Children of Men‘s most emotionally heated and technically impressive scenes is a real filmmaking marvel. Ultimately, it gives the film a much bigger punch because we are able to experience these scenes uninterrupted, with no disruption to the sense of time. Yes, these long takes give the film an almost “realistic” quality. And that is what separates Children of Men from the rest. There is not only good entertainment to be had with Children of Men, but a valuable learning experience. So yes, long story short: see this movie.