Williscroft lost control of his NASCAR-style Pontiac Grand Prix Stock Car while at high-speed on the back straight in slippery conditions during the fourth lap of the morning race.
The car spun on the wet grass and made heavy contact with the earth-filled tyre barrier on the right side of the circuit.
While Williscroft walked away, the car and the tyre wall were heavily damaged, resulting in the race being red-flagged and eventually declared.