We had to wait 10-15 minutes to exit the car park as although I had prepaid for parking the barrier wouldn't lift. When the call was finally answered my booking was checked and I was told the camera did not recognise 'private registration plates'. Then when I asked about a complaint procedure the operator then told me that I had no reason to complain! My number plate is correctly displayed in a legal format and font so I do not understand why it should cause an issue. I hope that this issue can be resolved as I do not want to delay the queue and my journey on exit every time I prepay to park in the airport car park.