Round, white sphere, moving at incredible speed, stopping and moving at right angles.My wife and i were lying by the swimming pool. I was looking up into the blue sky, and i saw what i thought was a white bird, at high level, but it was round in shape and the sun was reflecting at the back of it. It is difficult to judge the height, and the size of the object.I would have thought that it may have been a ballon or similar, except it moved at incredibaly high speed. It stopped for a few seconds, then moved off at right angles, stopped again, then moved back in the opposite direction, again at incredible speed. It then moved out of view, and we lost sight of it in the clouds.