End of the road for London's 'dirty' diesel buses
London mayor Sadiq Khan has announced "dirty" diesel double-decker buses will be phased out from the capital's current bus fleet from 2018.
It comes as the mayor unveiled London's first double-decker hydrogen bus.
Mr Khan also said all new single-decker buses operating in central London would be electric or hydrogen.
City Hall believes "greener" buses will reduce air pollution in the capital, long exposure to which is estimated to cause 9,400 premature deaths a year.
The mayor wants all London buses to meet the Ultra-Low Emission Zone standard by the end of 2020.
At least 20 new hydrogen buses will take to London's streets as part of a £10m part-European Union (EU) funded project supporting hydrogen technology.
Transport for London (TfL) will also provide at least £5m in funding.
The new hydrogen double-decker buses will be trialled on London's roads next year while a further 300 "zero emission" buses will be on London's streets by 2020.
Eleven other major cities - including New York, Los Angeles, San Francisco, Amsterdam, Copenhagen and Cape Town - also plan to phase out diesel buses by the end of 2020.
Paris, Madrid and Mexico City have committed to removing diesel buses from their cities by 2025.
Mr Khan, said: "I want London to become a world leader in hydrogen and electric bus technology.
"Transforming London's bus fleet by accelerating the introduction of zero-emission buses is important and I plan to work with bus manufacturers, other cities, the European Commission and the C40 Climate Change Leadership Group of Cities to move this agenda forward."