Heathrow has launched an investigation after a USB stick was found in the street containing security information.

The stick had 76 folders with videos, maps and documents some of which were marked as “confidential” and “restricted” but could still be read.

One document included details of measures used to protect the Queen.

The Sunday Mirror said a man found it in west London and handed it into them.

Heathrow said all of its security plans had been reviewed and the airport was secure.

“We have also launched an internal investigation to understand how this happened and are taking steps to prevent a similar occurrence in future,” it said.

Some files showed the types of ID needed to access restricted areas, a timetable of security patrols and where CCTV cameras were located.

The statement from the airport added: “The UK and Heathrow have some of the most robust aviation security measures in the world, and we remain vigilant to evolving threats by updating our procedures on a daily basis.”

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