An unemployed London man discovered a USB flash storage device lying on the street as he was headed to the library to check the Internet for job listings. When he got to the library, he plugged it in and found it was filled with security details for London's Heathrow International Airport—including security measures and travel details for Queen Elizabeth II. The man turned over the drive to a reporter at the Sunday Mirror.

On the flash drive were 76 folders of files, including security documents and maps of the airport. The maps included the location of every closed circuit television (CCTV) camera at the airport; routes and security protection measures for the Queen, Cabinet ministers and visiting foreign dignitaries; and maps of the airport's tunnels and escape shafts for the Heathrow Express train station.

Other documents included a timetable for anti-terrorism patrols at the airport, a documentation of the ultrasound system used by Heathrow security to check perimeter fences and runways for breaches, and details of the types of identification required to gain access to secure areas—including those used by covert security personnel. There were also photos of the security facilities used by the Queen.

In all, the drive contained 2.5GB of data—all of it unencrypted. In a statement to the press, a spokesperson for Heathrow said:

Heathrow’s top priority is the safety and security of our passengers and colleagues. 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. We have reviewed all of our security plans and are confident that Heathrow remains secure. We have also launched an internal investigation to understand how this happened and are taking steps to prevent a similar occurrence in future.

London Metropolitan Police were working with airport officials to determine how the data found its way out of the airport's offices.

The news comes as the United Kingdom remains under a severe-level threat alert for both international and Northern Ireland related terrorism from the UK's Security Service (MI5). This was a reduction from the critical level alerts issued in September after the bombing of a train at the Parsons Green Underground Station.