UFOs are by very definition impossible to define, we have no idea what they are. Just because something is called a 'UFO' does not make it an alien, it could be a drone, a break in the clouds or a duck with a flashlight on its head.
This footage was caught from BBC London and shows what appears to be a strange light appearing in the distance as a man is talking to the camera.
We'll be honest: we have no idea what it is. There's every possibility that it's an error on the camera, or a problem with the transmission.
If it isn't either of those, then the answers start to get a little stranger. Best guesses on a piece of paper by the end of the day.