The builders of Britain’s ancient stone circles like Stonehenge were using Pythagoras' theorem 2,000 years before the Greek philosopher was born, experts have claimed.

A new book, Megalith, has re-examined the ancient geometry of Neolithic monuments and concluded they were constructed by sophisticated astronomers who understood lengthy lunar, solar and eclipse cycles and built huge stone calendars using complex geometry

One contributor, megalithic expert Robin Heath has even proposed that there exists a great Pythagorean triangle in the British landscape linking Stonehenge, the site from which the Preseli bluestones were cut in Wales, and Lundy Island, an important prehistoric site.

Pythagoras’ discovery that the sum of the areas of two squares on the sides of a triangle will add up to the area of a square on hypotenuse has been used for millennia to help builders attain perfect right-angles.