Heathrow's top-secret files dumped in London street
A memory stick containing sensitive Heathrow security data, including the Queen's route to the airport, was reportedly found lying in the street.
A total of 76 files on the drive contained maps and restricted documents, reports the Sunday Mirror.
The USB stick, which was discovered by an unemployed man in north London, detailed the exact route the Queen takes to the airport and her security measures, as well as those for cabinet ministers and foreign dignitaries, the newspaper said.
It also reportedly contained other sensitive information such as a timetable of security patrols guarding against terror attacks and the types of ID needed for restricted areas.
Heathrow spokesman said an internal investigation has been launched into the data breach.
The newspaper reported that the memory stick was handed to its reporters by a man who spotted it on the pavement in Ilbert Street, Queens Park, as he made his way to a library to search for work.
When he plugged the pen drive in, he was reportedly able to access 2.5GB of data, including 174 documents which were not encrypted or password-protected and some of which were marked "confidential" and "restricted".
Among data found on the memory stick were reportedly maps locating CCTV cameras and a network of tunnels linked to the Heathrow Express, as well as details of the ultrasound radar system used to scan runways and the perimeter fence.
A spokesman for the airport said security plans had been reviewed in light of the incident.
"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," Heathrow spokesman said.