What is the required safety clearance ?

Spannerdo

What is the required safety distance between units when queueing up to book into a CC site?

The reason I ask is that I wouldn't want to think that the CC might find themselves liable if someone who arrived either before or after me in the queue ( I know its unlikely but in peak season its the norm at many of the popular sites prior to the allocated
hour to dare to try to book in) might be inconvenienced by the small matter of either my or their outfit spontaneously combusting and the domino effect taking out the whole queue.

So in precis .....how much space must be left between your vehicle and the back of the unit in front of you if stuck in a queue on a CC site?