British police are investigating how a secret dossier that reportedly contained counter-terrorist plans for Heathrow Airport went missing.
The dossier, found lying in a road, showed 62 sites at the airport where al-Qaeda was most likely to launch anti-aircraft missile strikes.
The dossier apparently included facts about surveillance, escape routes, evacuation plans and deployment of rooftop snipers at the world's busiest international hub. The plans, which have since been returned to police, were found by a motorist.
A spokeswoman for the Metropolitan Police could not confirm whether the dossier was compiled by the SO18 anti-terrorist Aviation Security team, which is based at Heathrow police station.
Ten years ago, the IRA targeted Heathrow Airport with rocket attacks. None of the missiles packed with Semtex plastic explosive detonated.
Security chiefs sent tanks into Heathrow last year after intelligence pointed to a threatened missile attack.