LONDON, ENGLAND - OCTOBER 10: Caroline Pidgeon, Lib Dem Mayoral candidate, speaks during a rally against a third runway at Heathrow airport, in Parliament Square on October 10, 2015 in London, England. Before today's rally against a third runway at Heathrow, Parliamentary hearings were announced yesterday to investigate whether the increase in flight traffic will break toxic air limits. (Photo by Chris Ratcliffe/Getty Images)
