Yet another possibility - although maybe a more unlikely one? - is that this signals the return of the 'Sydenham Panther'.

There have been repeated sightings of an unidentified big cat in the area between Crystal Palace and Forest Hill over the last five years or so. Although this seems like the stuff of urban myth, not all of the witnesses could be written off as flaky self-publicists. I'm pretty sure that a poster on this forum has reported a sighting near their home in Netherby Road, which isn't that far from Stondon Park.

I can't cite chapter and verse on this but I remember that some of the online discussion/speculation on this theme referred to the remains of animals in Dulwich Woods that appeared to have been the victims of savage attacks by a large predator.

(The one thing that I do remember is a consensus that, even if there was a big cat roaming free around South East London, it was unlikely to be an actual panther, despite the local press giving it that title.)