The spectacular sight of the White Cliffs of Dover is guaranteed to bring a lump to any Englishman's throat but now geologists are set to reveal that they are just ancient dung piles.

Scientists have discovered that the chalk which gives the cliffs their distinctive white appearance is nothing more than the fossilised remains of mountains of shrimp droppings.

The discovery is due to be revealed on a BBC television programme this weekend, made with the help of Scottish Natural Heritage, the Government's nature watchdog. It is sure to damage the reputation of one of the world's most famous landmarks. The Scottish presenter of Postcards from the Past programme will also tell of the theory that the same tiny shrimps which made the chalk cliffs were partly responsible for the extinction of the dinosaurs because their flatulence caused acid rain.

The microscopic shrimps, called copepods, were once one of the most common creatures on the planet. They lived in the warm, shallow oceans of the Cretaceous age, around 100 million years ago. Geologists have known for years that chalk was made up of billions of algae skeletons, but they could not work out how the normally buoyant shells sank to the sea bed to form the rocks. Now the answer that will shock every Englishman, and surely spawn a new football chant for games against the Auld Enemy, has been discovered.

Postcards from the Past's presenter Anna Grayson explains: ''Copepods ate the algae and then packaged the indigestible shells into bundles in their rear ends. These lumps of excrement were heavy enough to sink quickly to the sea bed in a sort of continuous snowfall. ''So the next time you are sailing towards Dover you can ponder on the fact that much of the glory of England is built on an enormous pile of copepod poo.''

While most of England may lie upon the faeces of long dead crustaceans, Scots will be relieved to hear that their country contains only a few small deposits of chalk, which are in the Western Isles.