He has worked as editor of Tribune, United Nations & Diplomatic Correspondent for Al Jazeera English, speechwriter to the Secretary-General of the United Nations, Ban Ki-moon, and Director of Communications for the International Commission on Financing Global Education Opportunity, which was chaired by UN Special Envoy for Global Education and former UK Prime Minister, Rt.
He has been a diarist for the London Evening Standard and has contributed to newspapers such as The Guardian, The Independent, The Times, the Daily Mail, and The National (Abu Dhabi), as well as New Statesman, Private Eye, The Oldie, Country Life, and the website Big Think (New York).
Seddon also reported regularly from the United Nations and from the White House, and has lectured widely in North America and the UK.
In 2003, Seddon was the first journalist to reveal that "extraordinary rendition" had taken place in the British Indian Ocean Territory island of Diego Garcia.
He repeated the claims for Al Jazeera English TV, shortly before the then Foreign Secretary, David Miliband, admitted that extraordinary rendition had indeed taken place on the island of Diego Garcia.
Seddon was also the first foreign reporter to broadcast live from Pyongyang, the North Korean capital, in 2006, soon after performing the first trans Atlantic 'live' from the United Nations in New York to Doha for Al Jazeera English TV at the time of that Networks' launch.
Seddon was elected to Labour's National Executive Committee as a Grassroots Alliance candidate in 1997, gaining the highest share of the vote.
In the 2001 General Election, Seddon ran for parliament in the safe Conservative seat of Buckingham, against future Speaker John Bercow.