Thousands of bus workers in London are on strike Friday in a dispute over bonus pay for working during the Olympics, their union said. Transport for London (TfL) said around a quarter of bus routes were running but "many routes were disrupted". Members of Unite union employed by 17 bus firms walked out for 24 hours from early today over a 500 pounds bonus. But some bus companies are operating as they were prevented from joining in after the firms won an injunction against the strike action. TfL advised people to check for disruption before travel. It is understood the workers going on strike represent about 85 percent of the total workforce. London Mayor Boris Johnson said the strike was "extremely frustrating" and added "I can only conclude that this strike is being driven by hardline trades union militancy and a desire to have a strike for political purposes."