A swindler posing as the owner of a jewellery store outside Paris has managed to steal a set of luxury pens and watches with the unwitting help of local police and a locksmith.

Police say that a 30-year-old man claiming to be the owner of a jewellery store a few blocks away called in at the police station in Enghien-les-Bains, a small town north-west of Paris, about midnight on Saturday last week.

The man, identified only as Yves, told the officers he had lost his keys and needed their help to get into the shop. They kindly obliged, calling in a locksmith to pry open the door.

However, the locksmith became suspicious after the man reached for the shop's display counters, grabbing a handful of fountain pens and watches - among them a Rolex.

The locksmith asked the man for ID but the burglar said he had left his papers at the police station. He then fled the scene, carrying with him booty worth more than $16,000.