In October 1967, Roger Patterson was out hunting in the forests around Bluff Creek in northern California, when he suddenly came across a most unexpected quarry: a huge, hairy creature, about 8ft tall which looked like a cross between an ape and a man.

Patterson had a camera with him and caught the creature (above) as it loped off into the undergrowth. The film was hailed as the first conclusive proof of the existence of Bigfoot, or the Sasquatch, a legendary creature from north American folklore.

Expeditions were mounted and further sightings reported, but film director John Landis admitted much later that the creature on the film was a hoax. It was, he said “just a suit made by John Chambers”. Mr Chambers was a Hollywood “monster maker” whose first claims to fame were the models for Planet of the Apes. Roger Patterson died before Landis’s revelation, still believing that he had seen a mythical creature in the flesh.

Elsie Wright and Frances Griffiths.

Frances and Elsie were cousins who lived in the tiny village of Cottingley in Yorkshire. One summer day in 1917, they took photographs of one another beside a stream, playing with a group of fairies or “nature spirits” as Frances called them (below).

Their families thought this was a girlish prank, but Sir Arthur Conan Doyle got to hear about the pictures and was much taken by them. In a war-weary world, there were many other ready believers and the rural idyll they depict continued to enchant. Until 1983 that is, when the cousins eventually came clean and admitted that they had painted the fairies on cardboard and stuck them on the ground with pins.

But Frances later insisted that although most of the photos were faked, one was utterly genuine and that she really had seen fairies at the bottom of her garden.

Eric von Daniken.

Mr von Daniken was a Swiss hotelier whose book Chariots of the Gods was a publishing sensation in 1969 when it first appeared.

It posited the theory that Earth had been a staging post for ancient inter galactic travellers and that monuments from the pyramids to Easter Island statues were no more than landing beacons for space craft.

The theories were enormously popular but regarded as nonsense by seasoned archaeologists. An expedition led by Dr Tony Spawforth from Newcastle University completely disproved his theories on the Peruvian site at Nazca, whose vast geometric doodles (left) are, according to von Daniken, a flightpath.

Dr Spawforth says that if that’s the case, why do the runways run up and down hills instead of across the flat of the plain, and why do some contain piles of stones, which would surely have got stuck in any aircraft landing gear? The British team claimed instead the lines are a two-dimensional plea to gods of the Andes to send more rain.

Von Daniken’s theories have nonetheless spawned an entirely new genre of “alternative archaeology”. A recent bestseller suggests that the pyramids were built thousands of years earlier than believed by - you’ve guessed it - a super-intelligent civilisation. Its title? Fingerprints of the Gods.