Government "rain-makers" used adapted gliders: http://news.bbc.co.uk/olmedia/1515000/images/_1516880_cloudseeder300.jpg
Thirty-five deaths in the infamous Lynmouth flood disaster came only days after RAF rain-making experiments over southern England, it has emerged.
Ninety million tonnes of water swept down the narrow valley into Lynmouth on 15 August, 1952, destroying whole buildings.
Now, a BBC investigation has confirmed that secret experiments were causing heavy rainfall.
Classified documents on the trials have gone missing, but people involved have told their story for the BBC Radio Four's Document programme.
I could never find anything of any consequence, except the fact that papers were clearly missing for the significant years
Tony Speller, former North Devon MP
North Devon experienced 250 times the normal August rainfall in 1952.
Survivors tell how the air smelled of sulphur on the afternoon of the floods, and the rain fell so hard it hurt people's faces.
The East and West Lyn rivers, which drop rapidly down from Exmoor, were swollen even before the fatal storm.
Wrecked street BBC
Entire buildings were destroyed
Trees were uprooted and formed dams behind bridges, creating walls of water that carried huge boulders into the village, destroying shops, hotels and homes.
Bodies washed out to sea were never found. Dilys Singleton lost six members of her family, including her grandmother.
She recalls: "Mum identified her by this huge wart on her back because she hadn't got no head, or arms, or legs when they found her".
Survivors called for an investigation into the causes, and rumours of planes circling prior to the deluge.
The seedsman had said he'd make it rain, and he did. It was not until the BBC news bulletin was read later on that a stony silence fell
Alan Yates, Operation Cumulus pilot
The Ministry of Defence has denied knowledge of so called "cloud-seeding" experiments during early August 1952.
Tony Speller asked to see Ministry of Defence files when he was MP for North Devon under Margaret Thatcher.
He said: "I could never find anything of any consequence, except the fact that papers were clearly missing for the significant years".
But the Document team have tracked down fresh evidence, including RAF logbooks and personal testimony.
"Operation Cumulus" was jokingly referred to by those involved as "Operation Witch Doctor".
Alan Yates, a glider pilot, tells how he flew over Bedfordshire as part of Operation Cumulus, spraying quantities of salt into the air.
Scientists told him it caused a heavy downpour in Staines, 50 miles (80 kilometres) away in Middlesex.
He said: "I was told that the rain had been the heaviest for several years, and all out of a sky which looked summery.
"The seedsman had said he'd make it rain, and he did.
"It was not until the BBC news bulletin was read later on that a stony silence fell on the company."
The team is still hoping for evidence that would clinch their case beyond all reasonable doubt.
Other flights may have taken place - possibly using silver iodide.
The British Geological Survey has done preliminary searches for remaining traces, with more planned next year.
"They have not found silver and iodide in the same place," a Document team spokeswoman said. "But if they did, we would have a massive story."
They hope for an answer in time for 15 August next year - when the people of Lynmouth will be marking the 50th anniversary of the great deluge.