The ES is now reporting it is a 13 foot hole rather than a 50' sink hole. And the video shows work just south of the station.
stannit link

I seem to remember a map with a old stream running from upper Sydenham down to the german bridge area which then continued towards Catford via the Perry Vale Rose gardens and Woolstone Rd. The contours of the area bear this out.

You can still hear the thing roaring underground by the bridge, but going by the man holes that run the length of the path by the rail, it was diverted and presumably now ducks under the rails by the PV car park.
I am guessing, but if that sewer failed, then it would eat a fair amount of soil pretty quickly.