“It smelled horrible.” Ken Willman, whose dog took an interest in an unusual rock at Morecambe beach, Lancashire when he came across the ambergris, told The Sun.

“I left it, came home and looked it up on the net. When I saw what it could be worth I went back and grabbed it. It’s like finding a bag of cash.”

Unemployed Ken Willman has already been offered £50,000 for the hefty six pound chunk of regurgitated puke, which resembles a rock with yellow patches.

“A company in France has offered 5,000 euros (£4,300) per 300g which would make my piece worth 50,000 euros (£43,000) but I’m told companies in Switzerland offer four times that amount,” he told Sky News.

Ambergris, also known as ‘floating gold’ or ‘dragon’s spittle’ is often used by perfume makers to make fragrances last longer by binding them to the skin. It can float on the surface of the ocean for years before washing ashore.

The rare substance is produced in the intestines of sperm whales, and is both waxy and flammable. It is usually passed out as faeces, but particularly large pieces are ejected through the whale’s mouth.

Main image: A sperm whale, recently (Thinkstock)

Watch an interview with Mr Willman below (via YouTube / BBC)