Strange Phenomena

Out at Carsington Water yesterday, I leaned my bike against a signpost whilst taking photographs which included the bike.

Note that the bike is almost vertical and that this is not a very good photograph, so I moved round to get a better shot.
As I pressed the button, my bike, for no obvious reason, fell over.

Shot 2 with the bike just falling over. The saddle had been touching the post a fraction of a second earlier. It was not windy, there was no-one else around, and I can see no reason for the bike to fall over, apart from the click of the shutter.  Very strange!