No, there are no Mercedes-Benz black cabs in London.
The iconic London taxi is the TX4 (and newer TX5/LEVC TX electric), manufactured by London Electric Vehicle Company (LEVC), formerly London Taxi Company (LTI), a subsidiary of Geely (China).
Key features:
Mercedes vehicles (V-Class, Vito) operate as private hire (minicabs) or executive chauffeur cars—not as hackney carriages (black cabs).