A hospital has admitted clamping ambulances for parking infringements and charging £50 for their release.
Security staff at King's College Hospital, south London, are clamping the non-emergency ambulances for spending too long in drop-off bays.

These ambulances are privately run ambulances who took up the contracts for patient transport. This is something that the LAS used to do in London, but then with the sneaking privatisation of the NHS the private companies started to do things cheaper and so the LAS lost a lot of these contracts.

They have, as far as I know, no exemptions to where they can park (unlike us proper emergency ambulances).

I'm not quite sure how "They clamp ambulances parked for more than an hour "to allow other vehicles into the area," works though, surely if they are clamped then they are still blocking the area?

I don't know, I'm an ambulance driver, not an ambulance parker. And if you've ever seen me park, that much is pretty obvious.