Next time you're wandering along a beach, keep a eye out for any unusual looking rocks.

That's what Gary and Angela Williams did - and they found one that could potentially be worth up to £50,000.

However, its no ordinary stone - it's a large piece of ambergris, or "whale vomit", which is used in the perfume industry

The couple, from Overton in Lancashire, were walking along Middleton Sands beach near Morecambe Bay on Sunday when they spotted an odd looking lump at their feet smelling of rotting fish.

Gary described the discovery as a "bit of a shock".

"It was down a section of the beach where no-one really walks," he told reporters.

"It smells too bad though. It's a very distinctive smell, like a cross between squid and farmyard manure.

"It feels like a rock hard rubber ball. Its texture is like wax, like a candle.

"When you touch it you get wax sticking to your fingers."

Ambergis is produced by sperm whales, which eject it into the sea when they have a stomach or throat problem.

It can float around undiscovered for years in the water, where it hardens and develops its distinctive odour.

Gary and Angela are now speaking to potential buyers in New Zealand and France, and hope to get a good price for their find. Another lump of Ambergis found Morecambe in 2013 was valued at up to £120,000. 

"If it is worth a lot of money, it will go a long way towards buying us a static caravan," said Gary. "It would be a dream come true."

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