I think it's a lot more than a deterrent. The company running it, called something like Smart Parking, is a member of the British Parking Association and will therefore have access to the DVLA database. So it looks like a number plate recognition set-up.
I gather the charge for overstaying your two hours isn't £60 - it's £90.
And as for this.....
I very much doubt that they'll enforce it. People in Marple tend to ignore parking restrictions anyway.
....I think Harry and 'people in Marple' have got an expensive surprise coming just in time for Christmas!