As I've said a few times, in this thread. The odd pairing over the years, yeah, very feasible. A thriving population of regularly breeding big cats, no.
But just to put things into a bit of perspective, as to people banging on about pics off people's mobile phones, or whatever, and this is just my thinking, might be very wrong, but, weren't there more frequent sighting in the late 70's and early 80's, when due to the dangerous animals licence, there were more cats 'set free', and obviously a few escapees, add to the fact that NO-ONE would've been able to take a pic of one on their mobil