Princess Beatrice has reportedly had her BMW stolen after leaving the car unlocked with the keys in the ignition.
If the report turns out to be true, she may struggle making a successful car insurance claim.
Police are now investigating after the £17,000 black 1 Series, which was a 17th birthday present from her father, Prince Andrew, was stolen in central London.
The 20-year-old princess, who has a police protection officer, was often seen driving the car, which has a personalised number plate, alone.
A Metropolitan Police spokesman said: "Westminster Police are investigating an allegation of theft of a motor vehicle. It has not been recovered at this time."
The spokesman did not confirm whether the car was left unlocked with its keys in the ignition, but said no arrests had been made and inquiries were continuing.
A spokeswoman for Princess Beatrice's mother, the Duchess of York, said it was a police matter and declined to comment.
© Press Association 2009