The Commonwealth Secretariat was established by Commonwealth Heads of Government in 1965 to be the main inter-governmental agency and central institution of the Commonwealth of Nations. 

It is responsible for facilitating cooperation between members; organizing meetings, including the Commonwealth Heads of Government Meetings (CHOGM); assisting and advising on policy development; and providing assistance to countries in implementing the decisions and policies of the Commonwealth.
The Secretariat is headquartered at Marlborough House in London, the United Kingdom.