Mild-mannered and cautious, Hans Blix is a former diplomat who ended his distinguished career clashing with George W Bush and Tony Blair over the decision to invade Iraq.
Born in Uppsala, Sweden, his career spanned 40 years, over which time he gained a reputation for his calmness.
He studied at the University of Uppsala, at Columbia University, and then at Cambridge, where he received his PhD. In 1959 he became a doctor of law at Stockholm University and was appointed Associate Professor in international law. From 1963 to 1976, he served in the Swedish foreign ministry, and in 1978 became Sweden's Minister for Foreign Affairs He was on the Swedish delegation to the Conference on Disarmament in Geneva for 20 years before becoming head of the International Atomic Energy Agency in 1981.
It was in this position that Dr Blix, 78, started a long and often turbulent relationship with Iraq as he tried to determine the extent of the regime's nuclear aspirations and capabilities, however, the Iraqis managed to hide an advanced nuclear weapons development programme from the IAEA - it was only discovered after the Gulf War in 1991. Dr Blix recently said of the errors: "It's correct to say that the IAEA was fooled."
The author of several books on international and constitutional law, Dr Blix stepped down as head of the IAEA in 1997 and retired.
Despite his retirement, in 2000 he was asked by Kofi Annan, the Security General of the UN, to lead the UN Monitoring, Verification and Inspection Commission monitoring weapons of mass destruction in Iraq.
The chief UN weapons inspector, he presented a report to the UN Security Council in February 2003, knowing his work was being undermined by pro-war politicians in the US and UK.
He criticised the September 2002 dossier, in which the Government tried to prove Saddam Hussein was a risk to Britain, as "hyped and spun" and expressed doubts that Iraq could employ chemical and biological weapons in 45 minutes.
Just last month he told a Danish newspaper, that Iraq was a "pure failure".