The AA says that with restrictions and rulings varying widely from one authority to another (and with 34 separate authorities including Transport for London drawing up their own rules for London, alone), motorists should check on websites before deciding where to park. This especially applies in London on royal wedding day, where some authorities will observe bank holiday regulations and others won't.

"Drivers need to keep a very wary eye out for wheel clamping signs as the clampers are still around and won't be made illegal until legislation is finally enacted in Parliament this year," said Bosdet. "Even stopping to turn round or check a map may be sufficient opportunity for a cowboy clamper to block in a car and clamp it."

Added Paul Watters, head of AA Public Affairs: "With legislation going through Parliament to outlaw clamping on private land, bank holidays and the royal wedding offer the cowboy operators one of the few remaining golden opportunities to extort hundreds of pounds from holiday drivers. They will seize their chance."