[brabel]

No idea about the UK, but in Brazil, in a highly populated area between Sao Paulo, Minas Gerais and Santa Catarina, in the mountains where rainforest is still preserved (Serra do Mar and Serra da Mantiqueira), it's know that there are big cats (locally called onça). This video shows some great footage: https://www.youtube.com/watch?v=VeDfeGR_kxI

I lived in that area most of my youth (but not in the last 20 years) and was outdoors a lot. I've never seen one of these animals, and didn't know anyone that had seen one (except for the rare dead animal found in the woods, or live animal that got trapped somewhere like a farm shed in some faraway farm). They're absolutely masters in not being seen... so I don't doubt there could be a few in the UK and nobody manages to get a good look at them.

EDIT : for those saying the big cats are dangerous, to my knowledge they're extremely shy and stay the hell away from people. I would be surprised if they've been known to attack, let alone kill someone in the last several decades (they talk about that in the video, but it's in portuguese).