A man has been arrested after a CCTV camera captured him trying to buy a cigarette with a credit card and the device’s owner, the Metropolitan Police said.
The device, which was not activated when the card was used, was used to scan the card and pay for a packet of chips.
The card’s owner was arrested on suspicion of fraud, theft and obstructing police officers.
He is due to appear at Thames Magistrates’ Court on Friday.
A spokeswoman for the Metropolitan police said the device was being used for surveillance.
The Metropolitan Police was called to a store in the city’s north-west on Thursday night after the owner noticed an alarm on the floor of the store.
The alarm had been triggered by the card reader.
When officers arrived, they discovered the device had been taken from the store and the owner had been arrested.
She was released on bail pending further inquiries.
A spokesman for the card holder said the card’s credit card had been used to buy chips, but he was not aware the device that was being fitted to the card had not been activated.
He said: “It’s a common practice to purchase a card and use it to buy some chips.”
The Metropolitan police declined to comment on the incident.
They are investigating whether the cardholder’s credit account was compromised.