It was the stuff of nightmares. On a sunny day in the mountains near the Great Wall of China, a lone hiker turned a corner to find a mysterious creature with bronze skin and long drooping ears squatting by a pool of water.

As the blood drained from his face, he summoned the presence of mind to snap a photograph so that he could post the creature on the Internet.

The gollum duly went viral. After the photograph was posted, it was reposted more than 30,000 times and gathered 24,000 comments. Some suggested the creature was an alien, others wondered if it was half-man, half-pig.

The image inspired rambling flights of fancy; long stories of the childhood of the beast, orphaned in the wilderness, or descriptions of its ancient lineage.

But later, a more mundane explanation emerged. An actor posted more photographs of himself being made up and posing as the creature while shooting an advertisement.

"This was an actor wearing a costume," clarified Beijing's police. "He was filming an advertisement."

"The actor has provided pictures of himself in the costume to prove it," added the local government of Huairou, the county where the hiker took his snap. "The actor was taking a loo-break and was still wearing his costume".

Additional reporting by Adam Wu

The Daily Telegraph