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, Leonard Morrison, a marine physics professor who has based his career on believing that the
Thames barrier was built in the wrong place, disproves Hopkins' theory with his independent but sophisticated computer model - which predicts that the storm and spring tide would merge to form a 46 metre-high surge. After a series of mis-informed meetings with
Deputy Prime Minister Campbell (who becomes outraged at the inaccurate forecasts) Hopkins feels guilt ridden as valuable time has been wasted. During a last-minute meeting at
COBRA (Cabinet Office Briefing Rooms) in
Whitehall, the authorities realise that
Central London would be inundated in three hours. Campbell declares a
state of emergency, which on the short notice causes severe panic and congestion in the city. As the COBRA authorities and military forces struggle to evacuate over one million people from the city,
Police Commissioner Patricia Nash is designated the emergency coordinator by Campbell and works with the rest of the team, 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 swamped 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 meet two maintenance workers, Bill and Zack, but when the surge floods the station, Bill drowns whilst sealing a door to save everyone else. The group escape to the surface via a vertical shaft and find 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 recede. 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 dies by 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. As the air strike is aborted and the floods recede, Rob is consoled by Sam as Morrison's body is recovered, who is among the over 200,000 casualties in the disaster. Campbell holds a radio broadcast to the survivors in the city, assuring them that London will survive and recover. ==Cast==