By Caroline Briggs
Entertainment reporter, BBC News
Clive Owen stars in Children of Men, a chilling tale of an apocalyptic world in which women can no longer have babies.
The year is 2027 and a litter-strewn London is under siege from terrorists, illegal immigrants and rising civil unrest.
The youngest person in the world has just died. Diego Ricardo was just 18 years, four months, 20 days, 16 hours and eight minutes old.
Clive Owen plays reluctant anti-hero Theo in Children of Men
While news of his death is greeted with Princess Diana-like mourning, a miraculously pregnant refugee turns up, who may just save humans from extinction.
Former political activist turned disillusioned bureaucrat Theo, played by Owen, becomes a reluctant hero when he is drawn into helping the young African woman to safety.
Owen, whose previous films include Closer and Sin City, says the film works by turning today's issues of mass immigration, terrorism, the environment and infertility into reality.
"These are things that we are scared and concerned and worried about now, actually happening. It is like things are now, but worse," he explains.
"By talking about things that are really worrying us now makes it a much more relevant film than it might have been."
Theo finds himself in charge of helping pregnant refugee Kees, played by Claire Hope Ashitey, to the sanctuary of the Human Project boat and the scientists who are trying to save mankind.
"To me he is very undynamic, very reserved, and almost like a shadow of a human being," explains Owen.
"He is a guy who has given up and who is desperately sad about the world in which he lives.
"Through the course of the movie, his hope is reawakened."
One of the recurring features of the film is Theo's lack of suitable footwear - something Owen insists was important to his character.
"Alfonso, very wickedly, in the action sequences puts Theo in flip-flops, which shows a perverse sense of humour," he laughs.
"It was a very deliberate thing of Alfonso to get away from any sense of a cliched, heroic character.
Children of Men also stars Oscar-nominated actress Julianne Moore
"I'm there trying to help this girl, and Alfonso didn't want to suddenly look like, 'Here we go, we've seen this before, this is where the main character saves the day' feeling.
"By putting him in flip-flops and making him look like a complete alcoholic, out-of-shape mess, he avoided that."
Some scenes in the film - which also stars Michael Caine as an ageing hippy and Julianne Moore - were shot in long sequences using a handheld camera to give a realistic, newsreel feel.
"It was very bold and ambitious to do it," says Owen.
"There were some huge extended sequences that went on for a very long time and within that buses would be blown up, tanks, sides of buildings. It was all one shot.
"Everyone knows that if you mess it up in any way - that's me, that's the camera guy, that's anybody - it's a four-hour reset. So nobody wants to be the guy who messes up."
The film was shot on location in a wintry London, and in a studio where the Sussex town of Bexhill-on-Sea was reimagined as a giant battle-scarred refugee camp.
Cuaron said that while the film was futuristic, he deliberately planted the images firmly in 2006.
"I wanted to do a film that was about today," explains the director, whose previous work includes Harry Potter and the Prisoner of Azkaban and the acclaimed Y tu Mama Tambien.
The film is set against a backdrop of terror and despair
"The whole idea was to bring the themes and subject matter that is crafting the first part of the 21st Century globally, and bring those subjects to the microcosm of Britain.
"We wanted the audiences not to feel alienated from today.
"Very early on when we were preparing the film, I went to the art department and said we are going to do a film set in 2027 and they got out all this futuristic stuff.
"I said, 'No guys, we are not going to need all of that stuff.' I got photographs from Iraq, Palestine, from Bosnia, from Somalia, from Northern Ireland and said, 'This is the film we are doing.'"