I captured it on video, youtube video link should be there. I saw a solid black object about the size of a car just sitting in the sky in Greenwich Park, it wasn't flying, just sitting there with a slight rotating floaty movement to it. It wasn't disc shaped, more of a donut shape but without the hole in the middle. After filming it for a few seconds I lost focus of it i think on my camera and suddenly couldn't find it, also couldn't see it with my naked eye, it had just disappeared. There was no clouds where it had been it was just gone.