If you hear the chopping sound of police helicopters in your neighbourhood, you might be wondering exactly what they are looking for - and now this footage reveals all.

The eyes in the sky above London are the National Police Air Service (NPAS) and work 24-hours a day to fight crime.

Whether it's a missing person, following a high speed chase, honing in on an escaping criminal or overseeing large gatherings in the capital, the force are keeping tabs on what's happening on the ground.

Video from behind the scenes shows the work carried out by NPAS as they respond to Metropolitan police calls.

What does the team do and who is in it?

The team has four members, all who play a vital part in maintaining the aircrafts and responding to police calls.

At the heart of everything that goes on, the team is supported by officers on the ground who respond to calls from boroughs needing assistance.

They help decide which calls the helicopters should go to and monitor weather conditions for flight safety.

The unit currently operates Eurocopter EC145 helicopters on a 24-hour basis

Engineers are also part of the team who not only carry out routine maintenance checks, but deal with any unexpected faults and failures to the aircraft and work around the clock.

Air observers are police officers who have completed an intense training course and probationary period to be part of the team.

They are responsible for controlling the helicopter’s video camera used to gather evidence, as well as assisting the pilot in navigating to incidents.

Watch on board with London's sky police

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After several months in this role, an observer can take a second course to become a Tactical Commander.

They are then responsible for the deployment of the aircraft, managing vehicle pursuits and organising ground units when called to an incident.

The pilots can be in the air for hours a time, and need to have the stamina and ability to multitask.

Whilst operating the helicopter, they must follow instructions given by the Air Observer or Tactical Commander, keep in conversation with police and Operations Officers on the ground and ensure all equipment inside is working.

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