I was taking pictures of Buckingham Palace from the bridge that crosses the Lake in St James Park. I took two pictures of the Lake with Buckingham Palace in the background. I took the two pictures one after the other less than half a second apart. When I downloaded the pictures to my PC. I noticed that there appeared to be an object in the sky above that palace. The object does not appear in any of the photographs taken before or after these pictures. It does not look like dirt on the lens. I was not aware of anything being there at the time I took the picture. The pictures are unedited in any way.