In a few years, the familiar hum of diesel engines powering London's black cabs will begin to be replaced by the whirring motors of more efficient vehicles. The London Taxi Company, which for time immemorial has built the overwhelming majority of the capital's Hackney carriages, today unveiled its next-generation hybrid vehicle. The TX5, which takes several design cues from taxis past, marries a four-cylinder petrol engine with an electric motor and "range-extended battery." The plug-in hybrid will also come with WiFi as standard and charging points for passengers, as well as six seats, more legroom and a panoramic glass roof. Currently, the TX5 is just a prototype, but the plan is to get these new vehicles on the road by the end of 2017.