To be honest I'm unsure as to current requirements but around 7 years ago when I was mad enough to risk it you didn't need any insurance , it's a private road, anything goes. It's pretty much the same rules as racing , if you crashed with someone else well, that's racing ..!!
As for track damage , By buying a ring card you accept the terms and conditions so if you crashed you are entirely liable for any track damage. You are charged from the minute they pick you up and they note every bit of damage. An example of how bad they are, a mate developed a small oil leak from his stator cover in the car park and an official tried to charge him for it .
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