Birds Of A Feather

Today was cold, wet and windy, when we travelled out to Addenbrookes Hospital for a morning appointment.  While we were there the rain eased up, so that when we drove home via Scotsdales Garden Centre, having stopped there for lunch, it was actually dry.  Even so it tried to rain a couple more times en-route.  Because of all this I had not had much opportunity to take any blips today, so immediately I got home it was out with the camera to see what activity there was in our garden.  The Squirrels had been on their feeder box and had scattered nuts about the grass beneath it and several birds were feeding upon these.  I took several pictures, through the window, but the only one which was sharp enough to display had a chaffinch and a regularly visiting pheasant upon it, so here it is.
 
My camera, a Nikon Df, turned on normally, but now refused to switch off not matter what is done to it, the only way to remove power from it is to take the battery out of it.  Has anyone else experienced this problem?  I have never had this problem with any camera prior to this.