I was walking along the canal towpath during the summer about 3 years ago, when I heard (or rather felt) this strange subsonic throbbing noise sensation. I looked over to the tower block on the opposite bank and saw an unusual object hovering in the sky. Emanating from it were what I can only describe as "distortion waves", which seemed to warp the space around the object. Luckily I had my camera with me and managed to capture the "UFO" and its effect on the tower block. The craft (or whatever it was) suddenly glowed a bright white colour and vanished! Well, it could have happened, but actually this is an upside-down photo of hanging willow branches and the reflection of the tower block in the water of the canal, with a leaf or something floating on the surface.