yes it happened few times with me. I just waited for 5-10 mins and then i dialed 999.
Tell them CAR'S REGISTRATION NUMBER and the police will call the driver of that car. If the driver doesn't pick up their call, they will send traffic police to give that driver a fine. Even they might even tow that car for you if necessary.
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I would suggest drivers that if for any emergeny, you have to park illegally or blocking other car's path, kindly leave your contact number on dash board by placing your BUSINESS CARD or any thing similar.

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There is a light at the end of every tunnel….just pray it’s not a train!./////*****