He underwent a brain scan, having been knocked briefly unconscious in the crash, which halted the race. The examination revealed nothing worse than bruising for the Hampshire man, who was later released and told to rest for a week.
Warwick's Alfa touched David Leslie's Honda on the approach to Island Bend. Both cars struck the barriers and, like Warwick, Leslie was unable to make the restart and the 10th round later in the day.
Rickard Rydell extended his lead in the championship with victory and second place in the day's two rounds. The Swede, driving his Volvo 850, took an unchallenged win in the first race of the day, but a poor start to the second allowed Alain Menu through to win for the Williams-Renault team.
"Making a good start was vital," Rydell admitted. "I made a good getaway in the first race, held off John Cleland's Vauxhall and just had enough of an advantage at the finish."
Cleland, who said he had tried hard to pass the Volvo "but it's a wide car," followed Rydell home in the second race, although the Swede in turn was unable to challenge Menu for victory.
The champion Gabriele Tarquini's return to the series ended in disappointment. An oil leak in the first race restricted him to 11th place and he crashed out of the second one when avoiding Julian Bailey's spinning Toyota.