LONDON, ENGLAND - DECEMBER 15:  The leader of the Green Party of England and Wales, Natalie Bennett, speaks to reporters during a meeting with  First Minister Nicola Sturgeon and the leader of Plaid Cymru, Leanne Wood inside Portcullis House on December 15, 2014 in London, England. The three met aiming to pledge to unite in their battle against Westminster parties, and call for the voices of all three parties to be heard in the General Election debates.  (Photo by Dan Kitwood/Getty Images)