A storm surge travels between the United Kingdom and mainland Europe, raising sea levels at the same time as the spring tide. Several parts of Scotland are devastated as a result, including Wick.

The Met Office's head forecaster, Keith Hopkins, mistakenly believes the storm will head towards the Netherlands. However, marine expert Professor Leonard Morrison, who has based his career on believing that the Thames barrier was built in the wrong place, disproves Hopkins' theory. Realising that London will be hit with a significant flood in just over three hours, the Government emergency management committee COBRA, led by Deputy Prime Minister Campbell, declares a state of emergency.

Over one million people must be evacuated from Central London before the water surge hits, creating many problems for the senior COBRA members to solve. Police Commissioner Patricia Nash is designated the emergency coordinator by Campbell and works with the rest of COBRA, including Major General Ashcroft, transport chief Johnson, and a guilt-stricken Hopkins.

Leonard travels to the barrier, where he meets his estranged son Rob, an engineer, and Rob's ex-wife Sam, the barrier manager. Sam oversees raising the barrier, but the tsunami arrives and overwhelms it. The flood sweeps into the city, destroying everything in its path. Rob and Sam jump into the Thames to escape the swarmed barrier, whilst Leonard is saved by a military helicopter and taken to Whitehall to advise COBRA.

Rob and Sam end up with other survivors in the London Underground. They are led through a ventilation duct to higher ground by two underground maintenance workers, Bill and Zack. When the surge floods the station, Bill drowns whilst sealing a door to save everyone else. The group finds a ventilation shaft and escapes the underground, finding themselves in the flooded Trafalgar Square, where Rob and Sam contact Leonard. They return with him to the barrier, where Leonard believes the water flow can be reversed back out of London, as the tide has turned and the water level is starting to go down.

General Ashcroft disagrees and lobbies the Prime Minister to authorise an air strike to destroy the barrier, hoping to create a surge to push the water back out of London. Hopkins, feeling guilty about the thousands of casualties, disappears and commits suicide. Nash clashes with Ashcroft, wanting to give the Morrisons a chance to remedy the situation.

Rob, Sam and Leonard discover the controls to initiate the reverse flow are now underwater. They realise someone can activate them, but they will likely die doing so. As Rob and Sam try to decide which of them should go, Leonard quietly makes the choice for them by going himself. He is successful in activating the controls but drowns whilst doing so.

With the barrier activated, Campbell orders the air strike aborted whilst Rob and Sam lower the barrier to let the water flow back out of London.

The film was shot on location in London for two weeks and in South Africa for 11 weeks.^[3] It is notable for the use of intricate production design and special effects in depicting famous London landmarks such as the London Underground, Houses of Parliament and The O2 being partially submerged under water.

Twenty-six studio sets were constructed with built-in water effects to shoot the actors in a wide range of flood sequences. Miniature sets in water tanks were used to shoot larger flooded buildings such as the Thames Barrier, London Underground and car parks. Computer generated visual effects were used to create shots of flooded London by combining shots of London with digitally created water. Locations in Cape Town were used for Whitehall, the Scottish coastline, London Underground and the Thames Barrier.

A 110-minute version of the film was given a limited theatrical release in the UK, premiering on 24 August 2007^[3] and was released on DVD in the UK in October 2007.^[4] An extended two-part TV version was screened on ITV1 on May 4 and 5 2008 and released in the UK on DVD October 2008.^[5] It also played as a mini-series in Lithuania, Spain, Italy, New Zealand, South Africa, Canada, Finland and Denmark. The extended version was repeated on ITV3 on 10 and 11 January 2009.

Critical response edit

Anna Smith at the BBC gave the film 3 stars out of five with the reviewer calling it "an American disaster movie on rather sodden British soil."^[6]

• Flood at IMDb  
• Flood at AllMovie
• Risques VS Fictions n°8, filmed interview (subbed in French) with Steve East, technical support team leader of the real Thames Barrier about the depiction of the barrier and scientific accuracy in the film.