I was processing a shot taken from the top of The Minster when I noticed a black spot in the picture (that was much larger than the one published).
I thought it could be some dust and I was surprised to notice it didn't look at all as dust, but as a metallic object in the middle of the sky.
It is not shaped as a plane, it can't be a baloon lost by a kid...
Another shot taken after 13 seconds (I'm slow in changing my settings, I know) has nothing at all in the whole sky.

What do you think it is?
Did I catch a UFO?

E.