|The `big cat` caught on film|
The grainy film shows what appears to be a 6ft-long beast slinking menacingly around a field near Stroud, Gloucestershire.
It was captured just three miles from Woodchester National Park - where earlier this year the mutilated carcass of a roe deer was found by a dog walker.
Despite the low quality of the never-before-seen footage, enthusiasts insist it is the 'conclusive' evidence that there are big cats on the prowl in the wild in Britain.
And they believe the particular animal in this footage shot by by Coryn Memory is the mysterious 'Wildcat of Woodchester', which has been spotted dozens of times in recent the years.
Big cat expert Frank Tunbridge, 65, from Gloucestershire, said: 'I think this footage is pretty much conclusive.
'It is the best footage of a big cat ever filmed in the UK - showing what we believe is a slim, young looking black leopard.
'You can tell by the size of the animal - it is huge. We think it is about 2ft tall up to the shoulder and 6ft long including the tail, which is way bigger than a domestic cat.
'It also walks just like a big cat and has an extremely long tail. There have been literally hundreds of reports of big cat sightings in this area for years. This could just be the tip of the iceberg.'
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Ms Memory says that this footage was not the first time she had seen the cat, and said she had spotted it on five previous occasions.
She first spotted a large black animal crossing the field near her house in Thrupp, near Stroud, in July 2009.
It again appeared again the following evening and she searched online to try and work out what it might be.
It was then she discovered the stories about a large panther-like animal roaming the Cotswolds.
Later that year she saw it again several times, and took some shaky photographs of the cat in the snow, as well as images of cat footprints.
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The intrigued single mum then got in touch with wildlife explorer Mr Tunbridge - who loaned her a camcorder to use the next time she spotted the beast.
In July 2010 she finally caught the animal on film after spotting it skulking in a field 300 yards from her home.
Balancing the handheld camera on a pile of CDs, she managed to film if for ten minutes as the beast stalked across the grass.
It was captured running and walking, before slinking off into the undergrowth near woods, near Rodborough Common.
Mother-of-two Ms Memory who works as a teaching assistant in a special school, said: 'I was fascinated just watching it walking around the field.
'I was not frightened at all - just excited to see it and finally get it on camera. It was only about 300 yards away.
'I believe he was looking for voles and mice in the short grass after it had been cut. At one stage a fox was in the same shot so you could compare the difference in size.
'The "Wildcat of Woodchester" was spotted only just a few miles away from here so I do believe it could be the same animal.
`It looked quite calm and not the snarling big cats you usually see in pictures. I haven't seen it since but I now really believe that these creatures are out there.
'I had never really heard of any big cats in Britain before I started spotting this one - now I know of loads of people that have seen it around here.'
Ms Memory, who lives with son Ashley, 20, and daughter Emilie, ten, handed the footage to Mr Tunbridge, who approached wildlife filmmaker Mark Fletcher and the pair began work on a documentary about the elusive creatures.
The team used imaging techniques to estimate the size of the black cat as 2ft high to the shoulder and 6ft long, including a 2ft tail.
They finally decided to release the pictures yesterday - after the devastated carcasses of three roe deer and three wallabies were found nearby last month.
DNA was taken from the first deer, which was found by a dog walker on January 4 this year.
The body had all of its vital organs missing and had its snout severed - the hallmarks of a panther-like kill.
Source: Daily Mail