A cinema-goer said staff nabbed two children aged around 10 or 12 as they tried to video Prisoner of Azkaban in a cinema in north London on 31 May.

He said: "It was so obvious, because they were carrying a small suitcase."

A spokeswoman for the cinema said they weren't aware of any incident, but said it was possible the kids hadn't been punished because they were so young.

Meanwhile, some cinemas are employing ushers with special night-vision goggles to spy any potential Potter pirates.

"We've already received positive feedback from cinema-goers when explaining what these are being used for," said a spokesman for Odeon cinemas.

"Staff have also been briefed on patrolling the auditorium to check for any recording equipment and random bag checks may be carried out."

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