They're known for being talkative, but this time they let their actions speak louder.
Black cab drivers brought parts of central London to a standstill.
They were even more opinionated than usual - over U.S. car service firm Uber.
SOUNDBITE: Ian Parsons, Black cab driver, saying (English):
"If you've spent £40,000 to get a London cab, then somebody just at the click of the fingers can just have a little smartphone device and just drive any vehicle."
Part of the taxi drivers' protest centres around the meter. Only London's iconic black cabs are allowed to have one, and they're subject to Transport for London regulations. They say Uber's smartphone app works in much the same way.
Cabbies are calling for a level playing field.
Steve McNamara is General Secretary of the Licensed Taxi Drivers' Association.
SOUNDBITE: Steve McNamara, General Secretary, Licensed Taxi Drivers Association, saying (English):
"They tell us what vehicles to dri
