Four British climate change activists have been arrested after scaling the gates at Queen Elizabeth II's Buckingham Palace residence and locked themselves to railings in a protest demanding more urgent action to cut greenhouse gas emissions. The activists who remained chained to the Buckingham Palace’s gate for four hours used megaphones to call on the Queen to follow the lead of his son Prince Charles and take a stance on climate change. The group, from the Climate Siren environmentalist movement, wore T-shirts with the slogan "Climate emergency. 10 percent annual emission cuts" and chanted through a loud hailer. London's Metropolitan Police said the four had climbed up a gate at the front of the palace and secured themselves to it, sitting with their legs through the railings. The protesters unfurled a banner quoting a 2008 speech by Prince Charles, the queen's son and heir, warning over a lack of progress on tacking climate change. It read: "The doomsday clock of climate change is ticking ever faster towards midnight." In a letter to the queen posted to the group's website, the activists said they were carrying out their protest in the hope of drawing attention to stalled progress on environmental issues. "It is time that you and all public figures with influence followed the example of your son by speaking up loudly ... about the escalating threat of catastrophic climate change," the group said. The activists consisting of three men and a woman are now being questioned by the Metropolitan police that said they are suspected of breaching the Royal Parks regulations. The Climate Siren said it timed the protest to come after the United Nations Sustainable Development conference in Brazil, Rio+20, where leaders and representatives from over 100 countries gathered to discuss development and ensuing risks to the environment. The group slammed the conference for its "failure to achieve any meaningful results".