Recent changes are now enforcing the 3 hour time limit in a very aggressive manner by a carparking enforcement firm called G24The new camera poles and signage have totally destroyed the friendly atmosphere at these local shops. It's a real shame that the management Jane let the 21st century clampers onto the site.
There is lots of free on-street parking around Harpenden town centre. Be careful to look at the signs for the parking bays though - restrictions apply. Time limit is variable, from 30 minutes to 2 hours. No return within 2 hours.