PM's trusted advisor on key policy issues
Jonathan Powell was Chief of Staff to former Prime Minister Tony Blair from 1995 to 2007.
He was the only senior adviser to last the whole period of Blair's leadership. His role as the chief British negotiator on Northern Ireland meant he became a familiar name here.
Mr Powell's book, Great Hatred, Little Room: Making Peace in Northern Ireland, details the negotiations which finally led to the agreement which brought back power-sharing devolved government.
Mr Powell continued to be a key man for Blair and a trusted adviser on a wide range of policy issues. He was described by The Guardian as being "at the heart of all (Blair's) key foreign policy initiatives."
In 2007, Mr Powell joined Morgan Stanley as a full-time senior managing director of its investment banking division. In 2011 he helped found charity Inter Mediate, which works on armed conflicts around the world. Since 2013 he has also been a member of the Board of Save the Children International.
Last year David Cameron appointed Mr Powell as the UK special envoy to Libya to promote dialogue between rival factions in the country.