I saw a large black cat the size of an adult male leopard. But it's tail was shorter like that of a jaguar. Where the sun was shining on it's back, I could see a reddish tint to it's fur (which is a trait of melanistic leopards and jaguars) It was walking along the edge of a field near junction 10 (Reading, Berkshire) on the M4 motorway back in 2006.
My mother's friend had a very close encounter with what she called a 'skinny lioness' (puma) back in the early 2000s, near the Thames river where Eton meets Windsor. Said she was sat on a bench with her eyes closed meditating, when she suddenly felt she was being watched. So she opens her eyes, and sees this big brown cat walk across the clearing from one patch of woodland into the other, all the while staring at her. She was left shaken by the encounter, and refused to go walking in that area alone again.  
My mum saw a large grey cat as it was getting dark near Slough (next to the Langley country park). Said it was the size of a large german shepherd and was walking along the road as she drove up to it. As her car got near, it suddenly jumped off the road and bounded away towards the woods in the darkness.

A few years ago on the East Coast between Ingoldmells and Skegness I was walking along the sea front from Ingoldmells to the 24 hour garage at Skegness, half way there is a golf course, the moon was out and my night vision was alert, on one of the greens there was a fully mature Black cat, massive, I was with a friend and we both watched in fear as this cat stalked something it had seen, we watched for a minute at least and then made a hasty retreat both in shock and fear, we walked the main road way back, nobody believes this story but we will remember ir for rest of our lives

Me and my driving instructor saw a large black panther in Leighton Buzzard near Milton Keynes. It walked right in front of us while we were parked up and disappeared into some bushes near a field. These things are out there believe me.

i saw a big black cat in the north east of the uk around the size of a rotweiler it was around 4am coming home from a mates house i had to cross the field of a community sports centre when from behind a 5 ft gridded fence walked the "panther" its sillhouette was unmistakable as this thing was around 20ft away and back lit from street lamps it stopped and turned to face me we stared at each other for maybe 10 seconds and thats when i noticed its rounded ears and thick tail and i could see its shoulders as it lowered itself as it stopped to look before it walked thirty feet or so then jogged into the next fields trees. i reported it to police and they later confirmed 2 more sightings in towns either side of my town and a sheep mauling. this was early in the 2000's.This was in stockton on tees

Saw one in Cornwall early morning right in front of our motorhome, just making its way into thick bushes at the side of the road. It was black & had the longest tail, & definitely not domestic!

I grew up on the isle of wight and in 1995 I was walking to my sisters house on the edge of parkhurst forest late one night after a party and saw a big cat cross the lane about 100 yards in front of me. I often think back and question what I saw. At first I thought it was a black labrador because it was that kind of size but it was moving slowly and paused for a second and I'm certain it was a cat. It wasn't just the head but the tail which sticks in my memory, how long it was and how it was held, so distinctive of a big cat. Dogs and even domestic cats just don't have a tail like that. There was only one street light further back so I can't be certain of colour because I could really only see the silhouette but size and shape was unmistakable. I know full well I sound like a total crank writing this but I'm pretty sure I saw a big cat that night.

In the mid 1980's When i was a teenager, walking my dog deep in the woods off the beaten track,i got a bit lost, my dog was senting something in a tree,i looked up and saw a mangled small deer wedged in the tree. It looked partly eaten and it freaked me out. I and my dog felt fear and got out of the woods as quick as i could. Never told my parents they would not of believed me. It was an odd thing to come across.

I saw one in Thetford forest during the 90s. I was cycling along a track and looked down a forest fire road as I passed the end of it. I saw a large black cat about the size of a Labrador but shorter in the leg. It had a long curved tail almost as long as it's body.
I doubled back to get a better look but it was gone and my spider senses were getting twitchy.
A friend of mine came face to face with a lynx while cycling in East Suffolk too.

Spotted one in DONCASTER late 90s 😮

Go back some 40 odd years and one warm summer's night, I saw something at 0130 hrs in the morning.
I was in my MG MIdget with the roof down as it was warm (Even if it was cold but dry, I'd take the roof down. No point having a convertible in the UK if you're going to wait for those 4 days when it's sunny to go topless?). I digress. I was on the Worcestershire, Warwickshire border heading into Warwickshire.
I was driving in a very small village, turned right down a road that lead out of that village and something dark and large was running down the middle of the road. It did so for a good few seconds before it veered to the left. The grass curbs either side of the road was probably some 30 odd feet wide before the hedgerows.
Whatever it was, stopped by the hedge, turned towards me, then vanished through the hedge never to be seen again.
Now.
Some cynics will say, "It was just a Black Lab or Alsatian."
But I've had Alsatians in the past. My uncle always used to have Black Labradors. So whatever it was, did not run or move like those aforementioned dogs. Plus those dogs did not have the length of tail this beastie had. And as far as I've ever found out, they do not have it's piercing, night vision specialist, yellow/orange eyes. I had followed the beastie with full beam of the car by turning slightly to the left to follow it.
And no dog has ever given me that primordial fear that this beastie did. The hairs on the back of my neck, stood up!
I was being forewarned warned by some act of nature that I was NOT the alpha predator. It was then that I remembered I had the roof down. That made me drive off PDQ!

As for YOUR footage at the end.
Look at the cats forehead. Just between and above the eyes. There is a dark "M" pattern. That's the sign of a domestic tabby cat. sadly, it's nothing more. Nothing less.
But you've got me intrigued. So I've subbed to you  👍

Def. big cats in the UK. It's not even a question at this point. thnx

Scotland 2005 my cousin & I were driving on a very cold night around 11pm, we were going to see a relative. We were on a very quiet country road & we turned a corner & on the middle of the road eating roadkill was a very large black cat. The headlights hit its eyes & it jumped to the grass verge & disappeared. Absolutely beautiful it was & we could not believe what we had just seen. When we got to our relatives who lived near by, he was not surprised to hear what we had seen him being a local. I'm no expert but to me this was a large black panther, I feel very privileged to have seen such a beautiful creature here in Scotland.

I was in my car at dusk and had a large mountain lion cross through me head lights and watched vault a five bar gate

we had full grown sheep killed and vets reported that the cause of death for all was strangulation by a bite around the throat and claw marks across the belly. some carcasses were flayed. the vet report conclusion  was a large non indigenous feral cat.

Saw one about 7am one morning in Essex on the way to Clacton on Sea.  I also remember seeing, quite a while ago, CCTV of one walking across a garage forecourt in the middle of the night, but nothing more was ever seen or heard about it.  It was definately hushed up.

Ive seen one in kent reported looked black but was at dusk

People have been hunting these cats since the 1970s to my knowledge. Dartmoor for example is a huge piece of turf and a cat can see you miles away.

My sister saw a large black cat on the ridgeway in Oxfordshire (Wantage) around 2003

I live in cornwall , i have seen a fully grown black jaguar 10 metres away from my garden ,this was during lockdown , a year later i saw a juvenille , same colouration but a third of the size , it was still the same size as a medium dog !! I told people and fot funny looks , but a couple of the people i told have since seen the elusive creature !!

I saw one about 14 years ago in Lichfield, South Staffs. I was driving a taxi, it was just before midnight. I picked up a local careworker, regular customer. We had to stop the car as it was stood at side of road under a street lamp. It crossed in front of us… well, it stopped in the middle of my lane close to my bonnet, it squatted down and as good as dissapeared. It was black, large puma/ small lioness size. It did not have a leopard or jaguar build. I could see faint leopard/cheetah type markings faintly on its rear legs. It did seem a little disproportionate to me… its neck seemed too long, and its head undersized for its body. Its muzzle/snout (whatever) seemed quite long and thin. It did seem quite dishevelled, but it had been raining.
I mentioned this sighting to a guy online, who had seen one about 12 miles further north and he gave me a detail i hadnt mentioned… a very saggy stomach from having kittens.
I remember asking the customer “did you just see what i think i just saw” and she said dryly “what… that really big black cat like a puma or something”. 😂
There would not have been time to take a picture, but, at the time, confronted by such a thing, it didn’t even cross my mind.
It was a residential area too, although maybe 150yards away it was countryside and the Trent Valley trainline.