Thousands of taxi drivers brought part of central London to a standstill in protest at rival service Uber - a mobile phone app.
The drivers are angry about what they regard as a lack of regulation of the use of apps such as Uber.
The app works out the cost of journeys and cab drivers say it is the same as using a taxi meter, which only black cabs are legally entitled to use.
The Licensed Taxi Drivers Association (LTDA) also said part of the demonstration was about highlighting the length of training - between four and seven years - that taxi drivers undergo before being licensed.
He added that two drivers had been arrested and 10,000 drivers had attended the protest.
But Scotland Yard denied any arrests had been made and Transport for London estimated that about 4,000 drivers had taken part.
Organisations including the Rail and Maritime Transport union, London Cab Drivers Club and Licensed Taxi Drivers Association (LTDA) were represented at the protest. »