Pressure on parking space in town and city centres is now immense, hence the introduction of the congestion charge, now extended in London and possibly to be introduced elsewhere. But parking on private land, as opposed to the street, raises its own issues.
I'm regularly contacted by readers asking about their rights in relation to vehicles left by people who are not customers.
Unfortunately, pub car parks are often considered by many uninformed citizens to be public places where they can leave their cars without having to pay - and without having to patronise the establishment.
Town-centre pubs and those near railway stations have suffered for years from this misapprehension. Now, some of them are fighting back.
Clamping is not nice. It's an aggressive act - one Scottish judge called it "extortion and theft" - but it is increasingly used both as a deterrent and as a money-earner.
The town-centre landlord has a problem which he wants dealt with at no cost to himself if possible. The clamper has a wheel clamp and a persuasive way to extract money, apparently legitimately, from unauthorised parkers.
There are two important legal points about clampers. The first is that the clamper has to have the authority of the occupier to conduct his business. The trespass and/or obstruction is committed by the parker against the occupier. A pub car park is not a public place and persons use it only with the consent of the licensee or owner. Usually, this consent is implied, if you are a customer. It can be withheld, if you are not.
Enter the clamper. Polite notices having failed to deter the shoppers, and a manned barrier being uneconomic, the deterrent option is undertaken. A large, yellow notice in big letters tells the motorist that the car park is for customers' use only and that unauthorised parkers will be clamped.
This notice is crucial, because without it the clamping could be illegal, and the aggrieved motorist could sue for damages. He must be told, clearly, so that there can be no mistake, that he risks clamping if he parks in that area.
The car park itself must be clearly defined, rather than a vague area of open land that might or might not constitute a car park.
The notices should if possible be repeated, to avoid the possibility of the single notice being obscured by, say, a parked van. And there should be the instant opportunity of release, without undue delay, on payment of the fee.
Given all these factors, the High Court has decided that wheel clamping is lawful and can be carried out by occupiers such as pub landlords on their private land.
But the Government was concerned that those who have taken the opportunity to operate as clampers are both unregulated and at times threatening.
So it is now a requirement for those operating in the sector to hold Security Industry Authority licences, similar to those held by door supervisors.
From now on, it will be illegal for anyone to operate as a clamper without holding the necessary licence, and it will in fact be illegal for you to use clampers unless they are licensed - rather like using unlicensed door staff.
But the Government stopped short of introducing legislation to outlaw wheel clamping entirely. After all, it is now established as a legitimate weapon for police and local authorities against certain forms of street parking. The private sector has just taken its lead from them. But it requires a great deal of care and attention to the legal issues, not just a quick nod to a chap in the bar.