Mike gaskell says he witnessed 38 rolls in a meeting at Braintree on the 26th of august 1991.
Thats the most i've ever heard of although there was 36 at henham once in the 80's then 32 at braintree just a week after.
As for tarmac tracks there was believed to be 15-20 rolls at hednesford PRE 2000.
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R.I.P NuDgEr