Heathrow Airport officials have launched an internal investigation into how a USB memory stick containing the airport's security information was allegedly found on a London street by a member of the public, a spokesperson for the airport told CNN on Sunday.

The USB stick, which apparently held details such as the route which the Queen takes when using the airport and maps pin-pointing CCTV cameras and a network of tunnels and escape routes, was not given to police but instead was handed to a national newspaper, the Sunday Mirror.