(d) The Charter of the Commonwealth was adopted on 19 December 2012 and was officially signed by Queen Elizabeth II at Marlborough House, London, on the Commonwealth Day on 11 March 2013. The Commonwealth of Nationsis a voluntary association of 53 independent sovereign states, most of which were once part of the British Empire. The Commonwealth'* membership includes both republics and monarchies. The head of the Commonwealth of Nations is Queen Elizabeth II, who reigns as monarch directly in 16 member states known as Commonwealth realms.