"£100 parking fee for a 46 minute stay?"

I cannot fault the care provided at this hospital - treatment of our baby daughter's outpatient condition was handled well. My complaint is with the parking arrangement at this hospital whereby there are no entrance/exit barriers like all other NHS hospitals I have been to and very poor signage to indicate that this is a pay and display car park. For a 46 minute stay we received a notice today from "ParkingEye", a private parking management company, that I was to pay £100 for failing to purchase a parking ticket. This is extortion! I have disputed this based on poor signage. Photographing number plates without forewarning patients you are doing this seems like a breach of privacy which is deeply concerning for a NHS hospital such as Kingston.