'Helicops': Policing London from the air
8 November 2013 Last updated at 14:13 GMT
BBC Radio 5 live has been given exclusive access to follow the work of London's Metropolitan Police Air Support Unit for two weeks.
Based in north-east London, the unit has three helicopters, which fly for nearly ten hours a day.
As Stephen Nolan reports, their activities have included high-speed car chases, tracking suspects, and monitoring crowds at large-scale events including demonstrations and a fireworks display.
Video produced by Snappin' Turtle for BBC Radio 5 live
Nolan In The Air, BBC Radio 5 live, Friday 8 November, 10pm
More videos of the helicopters' work are available on the 5 live website.