The substance is highly valuable as it can be used to make perfume and is very hard to come by.

The dog came across a lump of valuable ambergris, which comes from a sperm whale’s intestine

Patrick said: ‘I work on a fishing boat, so I knew what ambergris was. I’ve never seen it before, but I’ve heard stories about it.’

Sperm whales can usually regurgitate food they’re unable to digest but when they can’t, they produce ambergris – a waxy secretion – to protect their intestinal tract from being damaged.

The secretion is then expelled. For many years it was thought it left via the whale’s mouth, hence it’s known as vomit, but scientists now believe it probably goes out the other end.

It will then float in the sea – sometimes for years – before eventually washing up on shore.

Patrick said he was walking along the beach when he ‘clocked something on the seaweed, and the dog ran over to it and dropped her ball’.

He added: ‘She doesn’t usually drop her ball, so I knew there was something there.’

When he got closer, Patrick saw it was a pale grey rock with brown and amber streaks and suspected it could be ambergris.

The 5oz lump of ambergris discovered by Patrick’s dog (Picture: Patrick Williamson/SWNS)

Ambergris – also known as ‘floating gold’ is sold by weight, with one chunk found in the Canary Islands this year weighing 21 pounds – and valued at £394,000.

To help determine whether a substance really is ambergris, you can heat a needle and lay it on the surface of the lump. If it melts into a waxy, black or brown liquid very quickly it could well be the real deal.

Patrick said: ‘We’ve tested it with a hot needle, and it was doing the exact same thing that ambergris would.

‘People have been saying that I can take it to Glasgow University, and they’ll test it – so I’ll be doing that on my next day off.’

He also weighed the lump: ‘It was about five and a half ounces. That’s not really that big compared to some other bits that have been found,’ he said.

The lump had washed up on Irvine beach in Scotland (Picture: Jeff J Mitchell/Getty Images)

Sperm whales are protected by law in the UK, however it is legal to sell ambergris discovered on the shoreline.

Patrick said people he knows are very excited about the rare find.

‘Everybody’s been messaging me – one of my pals even contacted someone at the local paper.

‘I’m not sure what I’m going to do with it!

‘I’m on the beaches all the time. I take my dog with me wherever I go, so we’ll be looking every time we land now.’

In 2015 a dog walker in Wales came across a 2.6lb piece of ambergris which was valued at £7,000 and sold at auction.