Under Transport for London (TfL) rules, all new black cabs from 1 January 2018 will need to be electric, or capable of producing zero emissions. Combined with an age limit for the cabs of 15 years, that means the last diesel ones should disappear from London by 2032.
From 2018
https://www.google.co.uk/amp/s/amp.theguardian.com/business/2017/jul/11/black-cab-turns-green-new-electric-london-taxi-levc-tx