There are indeed large cats, even panthers, which were kept as pets and were let go into the wild in the UK. There are some in England I believe which hunt deer, it is not uncommon to see wild panthers in the UK. I have a friend who said that there was a family back in the 60s-70s which had pet panthers, yes in Mid Wales, and they let them go into the wild (when laws became stricter) and about 10 or so years ago someone saw a few. It is not uncommon.