I came across this beauty whilst stopping for lunch in the west country on my way down to Cornwall. I have described this as a Box Sash Diamond Light which is something I have never seen before. The Diamond design is not unusual in fixed and opening windows but in a sash window it is. There would be a considerable amount of work involved in manufacturing and glazing of this window sadly now in a poor state of repair.
My guess is that eventually it will be replaced by a plastic unit, the building itself did not appear to be unusual or of historic importance so its probably not a listed building or window. I did knock on the door hoping someone would answer and throw some light on the subject but no one was in. So I stood in the public car park around the back of the building lodged between a parked car and an opening in a fence and done my best to take this image without drawing attention to myself. I did wonder what would I say if challenged by the police I would probably try and draw their attention to the design and aesthetics of this window and my website. They may come to a different conclusion! My wife incidentally wanted nothing to do with me at this point.