A prototype of an environmentally-friendly black cab, which runs on hydrogen fuel and lithium batteries, has been unveiled in London.
It can be driven for 250 miles (400km) on a full tank of hydrogen and produces no emissions other than water vapour.
Mayor Boris Johnson has set a target for manufacturers to ensure all London taxis are emission-free by 2020.
The prototype is not yet available to buy and will need further tests before it is allowed on the road.
Five of London's buses will run on the same system from later in the year.
"The black cab is a much-loved London icon, but it is also a significant source of pollution, especially in the centre of the city," said Kit Malthouse, the deputy mayor for policing, who also chairs the London Hydrogen Partnership.
He said the prototype was "an exciting glimpse of how hydrogen technology could soon play a vital role in cleaning up air quality".