An 18-month analysis by the National Counter Terrorism Policing Headquarters, which helps develop police policy, found the technology could be "transformative".

Police are also to take over investigations into drone misuse.

Following a successful trial at Gatwick airport over the past year, drones will be given to units guarding Heathrow, Stansted, Luton and City airports.

Selected airports in other parts of the UK will also use the technology.

The equipment will be rolled out over the next 18 months.

BBC London has also learned police will take responsibility from for investigating the irresponsible or illegal use of drones or unmanned aerial vehicles (UAVs) from the Civil Aviation Authority (CAA).

George Trebess from the National Counter Terrorism Policing Headquarters said it was also possible that drones could be used during major incidents, including sieges or standoffs involving firearms.

Speaking to security experts at the Counter Terror Expo in London, he said: "The technology is transformative.

"With the new system we will be able to carry out missions around seven times faster than ground-based activity and at around 10% of the cost. We estimate £1.2m would be saved in three years."

It is thought the savings would come through having fewer officers patrolling airports on foot.

source: BBC News