A military policeman spoke today of his shock after capturing dramatic footage of a big cat prowling close to a naval base.
Dog handler Chris Swallow, based in Faslane on the Clyde, said he saw a large black cat on a nearby railway line.
Pc Swallow initially believed he was looking at a Labrador dog crossing railway tracks from a friend's garden on the Churchill Estate in Helensburgh on 30 June.
But on closer inspection he said he became convinced he had seen one of the mysterious big cats which reportedly roam the UK.
"The animal wasn't moving the way I expected a dog to. It was then I realised that what I was seeing was a big cat," Pc Swallow said, adding that he was "stunned" by what he saw.
"I ran to my car to grab my mobile phone for a picture. I stood on the nearby rail bridge in Winston Road and got a still photo and a couple of minutes of footage of the animal moving up the railway line," he said.
"It was remarkable. I've heard stories about creatures like this moving about the countryside but never really believed them before.
"Looking back at the video I don't think there's any doubt that it's a big cat."
Big cats have been seen in the area before, with several reports of a large tan-coloured creature - the "Coulport Cougar" - in the woods and hills of Loch Long in Portincaple, Whistlefield, in 2004.
John Belshaw, HM Naval Base Clyde's pest control officer, said he was contacted by police in 2007 about the sightings.
"They asked me what I thought about the stories of big cats in the area and then told me they had seen one cross the road in front of them during the night," he said.
"I think they were quite shaken by the whole experience and wanted reassurance."
"I have had a look at Chris's footage and have to say that I do not believe it is a domestic cat or a dog.
"At one point in the video it seems to walk on the railway line and a dog simply wouldn't have had the balance to do this.
"You can tell from the size of the track that it is much larger than a house cat."
The naval base animal is just the latest in a long line of sightings of big cats in the UK - Cath Palug reportedly roamed Anglesey in the Middle Ages and sightings of the Beast of Bodmin have been regularly reported since the early 1990s.
Most wild cat sightings have been assumed to be panthers, with a handful of reports assumed to be the lynx - a big cat once native in this country.
Their existence in the wild has been accredited to a range of sources, from escaped zoo and circus animals to a mass release in the 1970s after the enforcement of the Dangerous Wild Animals Act.
Shaun Stevens, a researcher for Big Cats In Britain, a group which investigates animals roaming the British countryside, said the animal visible in Pc Swallow's photographs is "certainly not a domestic cat", adding that Argyle "appears to be a favourite haunt" of big cats.
The group hears of about 30 reported sightings of such animals in the area every year.
"I have a working theory that some of these cats may be a hybrid species or possibly a new species of cat," he said.
"Knowing that the width of the rail tracks in Chris's video is four feet, eight and a half inches, the animal photographed by him is clearly in excess of four feet.
"Initial first impressions are very exciting, as I think this could be one of the best pieces of footage of a big cat in the UK."