A protest on the roof of Parliament against the expansion of Heathrow has ended after almost three hours. Six campaigners who unfurled banners from Parliament were led away at about 1220 GMT. They were detained by police and are expected to be arrested. It is thought the group gained access to the roof via a fire escape. During prime minister's questions, Gordon Brown said decisions must be made "in the chamber of this House and not on the roof of this House". Police said there was a "strong possibility" the protesters had been guests of Westminster security pass holders. Waving The rooftop incident, which will raise fresh questions over security at the Houses of Parliament, started at about 0930 GMT. The protesters were led off peacefully and then searched by officers. This followed a similar episode on Monday, when banners were draped over a plane at Heathrow. These stunts are becoming tiresome and do nothing more than peddle inaccurate propaganda Matthew Knowles Society of British Aerospace Companies. During the rooftop protest, paper planes were thrown into the courtyard below. According to Plane Stupid, the organisation behind the demonstration, these were made from documents obtained under the Freedom of Information Act. A spokesman said of the third runway plans for Heathrow: "Two million Londoners face increased levels of noise, while CO2 emissions from the airport would shoot up despite claims by Brown that he's committed to fighting climate change." 'Becoming tiresome' But Matthew Knowles, spokesman for the Society of British Aerospace Companies, said: "These stunts are becoming tiresome and do nothing more than peddle inaccurate propaganda." It is seen as a fundamental part of British democracy that people should be able to go there to lobby their MP. The public are allowed temporary passes to some parts of the building, but to get to most parts of the Palace of Westminster it is necessary to have security clearance or...