Well, from what I am aware of (from my old manager who used to work in the Uni security), they dont actually have any clamps anymore (although they used to). I could be wrong, but Im pretty certain they are just detterents. And thanks to this site, my "Penatly Charge", and all accompanying letters, are being filed away under "Joke".

The university where I work (Surrey) uses them as well, and they are lying buggers! Got a "ticket" for not showing my permit, and was advised (by the university) that there was nothing I, or they, could do (despite the fact that they really wanted to help me, because they knew I had a permit)! They told me that it would be better to just pay it, before the charges went up. They also have appauling clamping signs, that I am pretty sure are un-enforceable as well. They read "No parking here (im paraphrasing a little) or we will clamp your car, and a fee will be required for its release" - end of sign, no other information regarding price, or how to contact them. I love my workplace *EDIT* Oh yes, and I think the parking tickets they give are verging on fraud. At the top of mine, it says (in big red letters) THIS DOCUMENT IS A PENALTY CHARGE. I am right in saying they cannot say this?