The driver entered the car park, one that he has used around 30 times a year for several years. In previous years the car park was run as one where you paid on entry, but this changed over the summer to one that you had to pay on exit having been taken over by Euro car parks.
He had parked there three times since and paid with no issue, however on this occasion he simply forgot to pay on returning to my car. There are no barriers that you have to go through to exit the car park, therefore this is very easy to do.
He realised his mistake the next day and attempted to pay for the parking via the app with no success. The app told me to contact customer services which he did by sending an email through their website explaining the mistake and offering to pay. He received an email a few days later stating that they do not accept retrospective payment, and today received the parking charge notice through the post.
He does not recall any signage between where he was parked and the exit.
What is the best approach to appealing this ?