If the terrorist atrocities of 9/11 and 7/7 are the defining moments of this young century, then Alfonso Cuarón’s Children Of Men could arguably be cinema’s most defining response.

Although in essence about a society falling apart due to the fact no children have been born for 18 years, Cuarón’s loose adaptation of P.D. James’ novel is more a parable on the fear of the ‘other’ that has spread since those dreadful events of September 2001.

It is also a story of hope and thinly veiled spirituality that sees former activist turned cynical salaryman Theo Faron (Clive Owen) embarking on a perilous journey of redemption to help save the human race from its own destruction.

Set in 2027 Britain, Theo is offered money by his estranged wife Julian (Julianne Moore) – leader of a radical group fighting to protect immigrants’ rights called the Fishes – to escort refugee Kee (Clare-Hope Ashitey) to the coast. Theo discovers just how important she is to the future of humanity, but must evade both government forces and terrorists if they are to survive.

Children Of Men is unlike any science fiction film you’ve seen before. While most sci-fi wallows in high concept special effects and extravagant production design, Cuarón adopts an immersive vérité style to show a London on the verge of collapse. The pre-credits scene sets up the film perfectly. As customers in a packed cafe watch TV with despair at the news of the death ‘Baby’ Diego, the world’s youngest person, Theo absent-mindedly buys his coffee and walks out onto a busy London street dominated by piled-up rubbish, run-down public transport and rickshaws. His apathy towards Baby Diego’s death saves his life, however, as seconds later the shop is torn apart by an explosion triggered by the Fishes.

The UK, as we learn from government propaganda proudly stating “only Britain soldiers on”, is one of the few countries that hasn’t tipped over into outright anarchy. Society nevertheless seems on the brink of collapse. Refugees desperate to flee the chaos that has gripped much of the world have landed on British shores, only to be met by a police state that “hunts them down like cockroaches”, according to Theo’s friend, ageing anti-establishment hippie Jasper Palmer (Michael Caine).

The masses are told to remain suspicious of immigrants (bringing to mind Cold War East Germany) and walk around in a ghostly daze seemingly resigned to humanity’s gradual extinction. This is nicely observed when Theo goes to see his government minister cousin Nigel who, when asked why he still ‘rescues’ works of art when no-one will be around to appreciate them, responds: “I just don’t think about it.”

Cuarón pointedly evokes the holocaust in such provocative and chilling images as refugees staring hopelessly out of caged buses heading for the nightmarish concentration camp located in the former seaside town of Bexhill. In addition, piles of burning cattle bring to mind the apocalyptic scenes seen in Britain during the foot and mouth outbreak.

The use of diagetic and non-diagetic sound is masterfully handled by Cuarón. The sound of attack dogs seems to echo in every frame, while John Taverner’s elegiac, passionately spiritual Fragments of a Prayer is introduced at key moments in the film.

Children Of Men isn’t devoid of humour, however. While society falls apart, ceremonial traditions such as the Royal Horse Guard’s trot down The Mall are still observed. Theo also wears a faded London 2012 top, which is given a blackly ironic twist as it would have been the first Olympics to take place after babies stopped being born. The film isn’t afraid to throw in a few fart gags too.

Owen has never been better as Theo, a reluctant hero who steps up to become Joseph to Kee’s Mary almost in spite of himself. The stellar supporting cast elevate the film, including the always-excellent Chiwetel Ejiofor as Julian’s right-hand man Luke, Ashley’s confused and frightened Kee and Pam Ferris as Fishes member Miriam, a former midwife who gets one of the movie’s most eloquent lines when she observes “very odd what happens in a world without children’s voices”.

Children Of Men‘s most indelible moments come during several bravura one-take shots. An ingeniously filmed chase sequence shot entirely within a car containing Theo, Julian, Luke, Miriam and Kee is chaotic, shocking and astonishing, while a tracking shot of Bexhill being turned into ground zero in the fight between government forces and the rebels is nothing short of extraordinary. You’ll be shaking your head at how Cuarón and cinematographer Emmanuel Lubezki pull it off.

Cuarón wisely avoids delving too directly into the causes of the mass sterility, although the theological subtext of the film (the struggle to ensure a child is born to save humanity from itself) suggests divine intervention. A truly astounding cinematic experience, Children Of Men is profound filmmaking that will shock and awe in equal measure.