Police are looking for two car hijackers, one of whom limped away after the vehicle crashed.
The thieves pounced as a 40-year-old man was about to get into his black Mazda MX5 at the junction of New Steine and St James's Street, Brighton, at 11.30pm on Monday.
They took the man's keys and drove off along the seafront.
The vehicle crashed into a lamp post on the A259 opposite Brighton Marina.
Detective Inspector Paul Fulwood said: "Officers were very surprised that they could get out of the car, let alone run off."
Brighton detectives are appealing for witnesses and want to hear from anyone who knows a man who has recently started limping.
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