Among Christian youth in the UK he is well known for his involvement in the "Peace Zone" at the annual Greenbelt Festival. He became internationally known, when he - as a senior volunteer of Christian Peacemaker Teams (CPT) in Iraq - was taken as hostage with three other CPT members, leading to a widely publicised hostage crisis. He had gone to Iraq to demonstrate his opposition to the invasion of the country by the United States-led coalition and to show solidarity with the Iraqi people.
According to his family, Kember went to Iraq to help Iraqis. Kember's family said: "Norman’s recent trip to visit the people of Iraq serves to highlight his willingness to listen to people from all backgrounds, beliefs, and walks of life and his determination to promote equality amongst all people." "He has gone to Iraq to listen, not convert; to learn from the Iraqi people, not to impose values; to promote peace and understanding."
On 5 December 2005 Kember's wife made a plea for his release. Her 30 second plea was shown on Arab broadcast station Al Jazeera. . A 10 December deadline was set by the kidnappers for the release of all Iraqi prisoners, or the hostages would be executed. It passed without any word on the hostages' fate.
As the deadline passed and with no news of his whereabouts his friends held an hour-long silent vigil for him in Trafalgar Square, London. A further vigil was held by local dignitaries and friends at Harrow Civic Centre. Two weeks later, with the Kember family still waiting to hear news, they set up a telephone line, hoping that the kidnappers would contact them.
On 5 March vigils were held in Trafalgar Square to mark 100 days since Kember was taken hostage. and on March 7 a new tape of Kember was aired on Arab satellite television station al-Jazeera. Three days later, the body of Kember's American colleague Tom Fox was found.
On 23 March Kember and the others were freed during a raid by multinational forces led by British Special Forces. None of the captors were present at the time of the raid, no shots were fired and no-one was injured. Professor Kember himself assumes that the non-violent manner of his release was a result of a previous campaign to get hold of one of his captors who obviously uncovered the address of the place in return for allowance to inform his comrades that they should stay away from the place.
He arrived back in the United Kingdom on 25 March and released a written statement saying "I do not believe that a lasting peace [in Iraq] is achieved by armed force, but I pay tribute to their (the armed forces) courage and thank those who played a part in my rescue". Later that day he also released a video statement in which he again thanked his rescuers, and those who had supported his family throughout his kidnapping.
Kember was repeatedly criticised for not explicitly (or explicitly enough) thanking the military forces involved in the campaign, but has requested the withdrawal of coalition forces from Iraq. General Sir Michael Jackson has told Channel 4 News that he was “saddened that there doesn’t seem to have been a note of gratitude for the soldiers who risked their lives to save those lives”. On 25 March, in a telephone phone-in discussion on BBC Radio 5 Live, Colonel Bob Stewart, a former British Commander under United Nations command in Bosnia from September 1992 to May 1993 suggested that Mr Kember and people like him were a liability, since he had ignored advice not to go to Baghdad and the security services, the British government and multinational forces had diverted valuable time and resources to rescue a "foolish, albeit well-intentioned, meddling civilian". The pretended lack of gratitude of his was criticised as not being characteristic of true Christian values.
Norman Kember has profoundly reflected on the time of his captivity and the circumstances of his release in the book "Hostage in Iraq" (published 2007). He himself considers it an irony that he travelled to Iraq to oppose the military intervention and was flown out of Baghdad in a military helicopter, guarded by machine guns. He also is discussing whether his peace testimony has been compromised and what alternatives would have been at hand. In lectures and interviews, Kember repeatedly pointed out that what saddens him most is the fact that he is alive and well, while people in Iraq, servicemen as well as civilians, are constantly threatened and many have meanwhile lost their lives. The more he feels compelled to advocate peaceful means of handling the conflict in Iraq and its consequences.