@Pale Rider I believe the Beavis case went in favour of Parking Eye, does this change your view? My son got one recently from Parking Eye and he's all for ripping it up.
The judgment has certainly tipped the balance in favour of the parking company.
It goes some way to establishing that a private company can charge a private citizen a 'reasonable sum' - in this case £85 - for over staying in a car park.
Practically, Parking Eye may still struggle to get the money from someone who refuses, or at least, it won't be cost effective for them to go to a county court in each case.
Mention is made on their site of a 50 per cent prompt payment discount.
If your son can put this matter to bed for forty quid, that might be a wise move.
No guarantee Parking Eye will pursue his case, but if they do, the chances are they will get a judgment in their favour.
According to the Supreme Court case press summary, their lordships linked Beavis with another civil dispute over the sale of a business.
I don't pretend to understand that case, but it shows the general notion of penalty clauses can be applied in other areas.
Those in this thread who were so keen for me to pay the ticket should take note - you might find yourself on the wrong end of a penalty when you least expect it.
https://www.supremecourt.uk/cases/docs/uksc-2013-0280-press-summary.pdf