Fire crews from Windsor were called to Barry Road after the car overheated and burst into flames.
Police and firefighters had to close the road at 8.40am causing huge queues as visitors tried to get into town to watch the parade and muster.
Watch manager Christopher Davis said: "It was a great inconvenience to everyone trying to use the road but we dealt with it as quickly as possible."The car was recovered and the road re-opened by 9.10am.
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Trains travelling to and from London Paddington are facing 'major disruption' this afternoon, with some services set to be delayed by up to an hour, cancelled or revised.