I hadn't heard that a London Taxi had standards to meet, but there are.
London taxi rules dictate a maximum width, as well as a famous 8.5-metre turning circle. The front tires have a 60 degree arc of movement to achieve that turning circle, instead of a typical SUV's 38 degrees
This new standard taxi is an electric hybrid with a 1.5 liter gas engine, will run for 80 miles on the battery, and compared to the last taxi running on diesel, will be far quieter, and emit less pollution. No doubt London will benefit from the reduction of both diesel exhaust and noise. Total range, 400 miles
The TX costs £55,559 (including a £7500 grant), but most cab drivers are likely to lease theirs at a set price of £177 per week over five years. That's a £10 increase on the lease price of the TX4, but the average driver could save £100 per week in fuel costs. Not to mention that service intervals are every 25,000 miles, rather than 12,000. It might be a compelling business case for cab drivers seeking an upgrade.
https://www.autocar.co.uk/car-news/new-cars/first-drive-levc-tx-taxi-streets-london (Thanks Steve!)