There is little question but that this object was hovering in the sky. It is not a bird or insect flashing past. It is not maneuvering like a plane or, for that matter, a surveillance drone. It's an unknown. The object appeared in central London, between the Houses of Parliament and the offices of MI6.
This is the comment left on YouTube by the poster:
Friday September 21st, approximately 4.15, in the vicinity of Lambeth Bridge (very close to Parliament, MI6 & MI5 HQ's and Central Communication Command, nerve centre for South London Policing.) Video shot looking North, about quarter of a mile South of the Thames. Object moved very slowly in a southerly direction, all the clouds in the sky were moving eastwards. Unfortunately i couldn't make out the obeject in the view screen as the sky was very bright in comparison. I stopped filming in order to move to a better position but the object had vanished by the time i got there.
Today, Monday 24th September, i spoke with a coffee vendor who runs a coffee stall on the Embankment next to Lambeth Bridge and he said other people had seen something also. Perhaps the most intriguing aspect of this is in the last miliseconds of the shot. What was the secondary object that flashed across the frame? Perhaps a missile launched at the first object? It is visible for only 3 frames or one tenth of a second.