Tuesday’s Leicester match was suspended due to stagnation.
The appointment, the most important of the season on the Midlands circuit, had not been doubted even during the night.
Shortly after 8am, officials called an impromptu inspection at 9.45am due to incessant rain all morning and not long after the inspection had taken place the decision was made.
Race director Jimmy Stevenson said: “Unfortunately he caught us in the act.
“When I arrived at 6 this morning it was fine, but it hasn’t stopped raining since and unfortunately it’s not suitable for racing.
“It’s a shame because it’s our most important appointment of the season and ITV was coming too.”