In scenes that may no longer be dismissed as far-fetched, a new film is to chart what would happen if the Thames Barrier was overwhelmed.
The movie, based on a book by Richard Doyle, imagines how London would look if it was deluged by a surge of water.
Flood, which features Robert Carlyle, was shot over 11 weeks last year.
The author has said he believes there is a real threat to the capital. He has called for the government to take "its head out of the sand".
Guernsey-born Doyle, who now lives on Dartmoor, wrote the book in 2003 after spending two-and-a-half years researching the issue.
Writing on his website Doyle says he came up with the idea for the book after reading an article on global warming.
"[It was] one of those terrifying pieces about more extreme weather, rising sea levels and frequent violent storms. Suddenly I remembered the Thames Barrier. I wondered how it would cope.
"I started to look into some of the details. Barrier height, tidal reports and so forth. The more I looked, the more concerned I became."
The film also stars Poirot's David Suchet and screen and stage actor Tom Courtenay.
Carlyle plays an engineering chief (Rob Morrison) who realises that his estranged father's worst predictions are coming true.
They have to put aside their personal differences to save London from destruction.
The film is due to be released in August.