The testing was undertaken apparently as a means of demonstrating that the new London Taxi Company product could perform in the sorts of hot, desert environments that some interested potential buyers are situated in (Dubai, etc.).
“On these trials, the vehicle successfully undertook daily of journeys of 300 miles, the equivalent of driving from Heathrow to central London some 20 times. This is roughly triple the average daily mileage of the typical London cab, reassuring cab drivers that there are plenty of extra-miles in the tank if they’re sharing the vehicle with another driver, or, should they land a popular ‘roader’ (London cabbie parlance for a long-distance fare).”
See https://cleantechnica.com/2017/06/11/london-taxi-companys-range-extended-electric-black-cab-beats-heat/ 
London Taxi Company’s Range-Extended Electric Black Cab Beats The Heat
London Taxi Company’s new range-extended electric black cab performs quite well in high heat conditions, as determined by recent comprehensive testing in Arizona, the company has revealed.
The testing was undertaken apparently as a means of demonstrating that the new London Taxi Company product could perform in the sorts of hot, desert environments that some interested