Britain’s Heathrow airport has launched an urgent inquiry after secret security information was discovered in files on a memory stick found abandoned on a street.

The documents outline routes and safeguards for Queen Elizabeth II, foreign dignitaries and top politicians using Britain’s busiest airport.

The USB drive also includes maps showing where CCTV cameras are located, and the escape route for the Heathrow Express railway serving the airport.

The memory stick was found by a man on Ilbert Street in London, around 10 miles from Heathrow, who took the device to his local library to study the contents. Other files, all unencrypted, describe the ultrasound detection system for protecting the perimeter fence and the runways, and detail the ID requirements for accessing every area of the airport.

He handed over the USB stick, containing at least 174 documents, to the Sunday Mirror newspaper, which informed Scotland Yard and airport intelligence chiefs.

“I was curious about what it contained, so a few days later, when I went back to the library, I plugged it into the computer. All these files were there. I couldn’t believe it,” the unnamed man told the newspaper.

Investigation begins

Metropolitan Police detectives are now liaising with airport chiefs to work out how the USB drive, with a massive 2.5 GB of data, ended up in the street.