Half of London's 5,000 police cars could well be electric or air-powered within four years in a bid to reduce carbon emissions in the capital, according to Scotland Yard.

The Met is currently trialling a number of electric Smart cars in addition to 140 Toyota Prius hybrids.

The electric Smarts have a top speed of 55 mph and can run up to 70 miles on a full-charge – perfect for the west end, but not really ideal for chasing gangsters up the M1, as you wouldn't get much further than Luton!

Ideal for policing London

"London is perfect for alternative fuels such as electric or hybrid vehicles," said Nigel Jakubowski, director of transport services for the Met.

"For central London, the top speed of 55mph isn't a problem. The uniformed officers who have driven them say they are very quick. We have installed charging points at the stations the cars are based in, and they work very well."