London - Nessie, the Loch Ness monster, is in fact an elephant, according to a Scottish palaeontologist who claims to have solved the riddle surrounding the unexplained sightings of a monster in a lake near Glasgow in Scotland.

Neil Clark, curator of palaeontology at Glasgow University's Hunterian Museum, who has spent two years investigating the myth, told The Times on Monday that the idea for Nessie was dreamt up as a "magnificent piece of marketing" by a circus impresario after he saw one of his elephants bathing in the loch.

In 1933, the same year as the first modern "sighting" of Nessie, Bertram Mills offered £20 000 in today's money to anyone who could capture the monster for his circus at Olympia, based in London.

Clark, who made a name for himself by discovering a 165 million-year-old dinosaur footprint on the Isle of Skye in 2004, said that the legend of the Loch Ness monster was "largely a product of the 20th century".

He said: "Most sightings occurred after 1933... All we have are eyewitness accounts, fuzzy photographs, distant video footage and proven hoaxes."

Most could be explained by floating logs or waves, but there were a number of unexplained sightings of a grey creature, with a long neck and humped back particularly from 1933.

"My research suggests that these were elephants belonging to circuses. Circus fairs visiting Inverness stopped on the banks of Loch Ness to allow their animals to rest", said Clark.

"When their elephants were allowed to swim in the loch, only the trunk and two humps could be seen: the first hump being the top of the head and the second being the back of the animal."

"The resulting impression would be of an animal with a long neck and two humps perhaps more if there were more than one elephant in the water.

"It is not surprising Bertram Mills offered a 20 000-pound reward to anyone who could capture the monster for his circus. He already had the Loch Ness monster in his circus", said Clark.

Nessie fans, however, have reported four sightings in 2005 alone. - Sapa-dpa