Gibraltar did not participate in the 1975 UK European Communities membership referendum the result of which had a direct impact on the colony. Neither did it participate in any European Parliamentary Elections between 1979 and 1999, but in 2002 legislation was passed by the British Parliament which allowed Gibraltar to formally take part in the 2004 European Parliament election as part of the South West England constituency in all subsequent European elections. Following the surprise election victory by the Conservatives in May 2015 it was announced that Gibraltar would fully participate in the proposed referendum on continuing EU membership, and this was legislated for in the European Union Referendum Act 2015. This meant that Gibraltar was the only British Overseas Territory in the European Union (EU) and uniquely it had the right to vote in EU elections and in referenda.