He was educated at Ampleforth College and Trinity College, Cambridge, and was an exchange fellow at Rice University.
He is the brother of Thomas Pakenham, Lady Antonia Fraser and Lady Rachel Billington. Pakenham was briefly a reporter for the Washington Post before joining the Foreign Office in 1965. He served in Nairobi and Warsaw before being seconded to the Cabinet Office 1971-1974 as Assistant Private Secretary, then Private Secretary, to the Chancellor of the Duchy of Lancaster (Geoffrey Rippon then John Davies), who at that time had special responsibilities for the co-ordination of British policy towards the European Communities.
In 1974 Pakenham was at the Commission on Security and Cooperation in Europe in Geneva, then was posted to New Delhi 1974-1978 and Washington, District of Columbia 1978–1983.
He was Head of the Arms Control and Disarmament Department at the Foreign and Commonwealth Office 1983-1987. Counsellor (External Relations) to the United Kingdom Permanent Representative to the European Community, Brussels, 1987-1991.
Ambassador and Consul-General to Luxembourg 1991-1994. And Minister in Paris 1994-1997.
Pakenham was then seconded to the Cabinet Office again as Deputy Secretary for Defence and Overseas Affairs 1997-1999, then Chairman of the Joint Intelligence Committee 1997–2000 (also Intelligence Company-ordinator 1999–2000).
Finally he was posted to Warsaw as Ambassador to Poland 2001-2003. He was made a Freeman of the City of London in 1992.
Since retiring from the Diplomatic Service, Pakenham has been chairman of Pakenvest International. Senior adviser to Access Industries. Non-executive director of the Westminster Group.
A trustee of Chevening House.
And a lay member of the governing Council of King"s College London (and its Vice-Chairman since 2009).