London taxi drivers brought Westminster to a standstill today in a protest over their ban from dedicated Olympics traffic lanes.
More than 200 black cabs arrived in Parliament Square just before 2pm blaring their horns to tourists' bemusement.
Their demonstration is targeted at Games' organisers who developed the so-called Zil lanes available only to Olympics officials, athletes and other approved vehicles.
Jonathan Myers, of the United Cabbies group union, said: "There will be no access to these lanes for any traffic apart from the Olympics family.
"Taxis are excluded, which is unacceptable and wrong. This is a working city and we need to get around and do our job."
Parliament Square quickly ground to a halt as the drivers descended on central London for what they plan to be a two-hour protest.
Traffic soon snarled up Whitehall, Millbank and over Westminster Bridge as car horns and traffic fumes filled the air.
Mr Myers said: "We've come to Parliament so MPs can wake up and hear what we're talking about."
He believed it would "absolutely impossible" for cabbies to carry on ferrying commuters around the capital during the Games when the full lane restrictions take effect on July 25.
Motorists who stray into Games lanes face £130 fines.
Mr Myers said: "London is going to be gridlocked and today we are showing them what it is like when it is gridlocked."
Taxi drivers plan further demonstrations on Monday and on July 27 - the day the Olympics officially open.
Mr Myers feared his members had been betrayed by officials who, he said, hailed the city's famous cabbies as one of the reasons London should be awarded the Games.
He said: "London taxis are held up as iconic throughout the world.
"It turns out the only people who think we are not are our own transport authorities."
Some competitors at the 1996 Atlanta Games missed their events because they were still stuck in traffic jams when the events began.
But Mr Myers branded as "complete rubbish" claims London athletes would be delayed and potentially miss events without the dedicated lanes, saying officials' "modelling was all wrong".
He hoped up to 1,000 cabbies would assemble in the square by 4pm, which would have a huge impact on tonight's rush hour.
Transport for London (TfL) criticised today's "completely irresponsible" protest.
Director of taxi and private hire John Mason said: "We have worked tirelessly with groups that represent the majority of hard working taxi drivers to provide cabbies with as much access to the lanes as possible.
"Through dialogue which started in 2009, TfL has secured concessions specifically for taxi drivers, including the use of turns along the Olympic route network that were initially banned for all traffic except buses, as well as access to a number of kerbside Games lanes to pick up passengers.
"We have informed taxi drivers that any such demonstration is completely irresponsible and would only disrupt the travelling public - the very people taxi drivers are supposed to serve.
"We strongly urge taxi drivers to ignore calls to join these unnecessary protests and instead show why they are regularly voted the best in the world."