you just turn up on the day and drive in. If your car is pre '70 you get in free. I told the chap on the gate last year the bug was a '69 and got waved through. I was lucky though, it only took me an hour to get out. There were reports of 4 hour waits to get out. What a ball ache...
I'm thinking of going for a couple of hours but parking down the road and cycling or walking to the show. Don't fancy the wait...