What is the mysterious black ring in this spectacular photo of London at night? [closed]

Here's another source for what appears to be the same photograph downloadable at higher resolution.

I think it's the parking lot (and row of trees next to it) encircling a bus garage. Here is a link to Google Earth (via Google Maps) zoomed in on it. The image is rotated relative to Google's map (north is not "straight up"), and, as someone else pointed out, the city is not seen from straight above but from an angle.

Wikimedia has a different one from the other direction which might lead to further insight (or intrigue).