Iraq posed little threat to Britain just before the 2003 war -- but the danger of extremist attacks surged following the conflict, the ex-head of domestic security service MI5 told an inquiry Tuesday.
Dame Eliza Manningham-Buller, chief of the intelligence agency from 2002 to 2007, also dismissed any connection between Iraq and the September 11, 2001 attacks on the United States.
She was giving evidence at Britain's public inquiry into the Iraq war, which has heard from figures including former premier Tony Blair, who was in power when the country joined the US under then president George W. Bush in the war.
Manningham-Buller said that in 2002, MI5 had advised Blair's government that the "direct threat" from Iraq was "low".
"We did think that Saddam Hussein might resort to terrorism in the theatre if he thought his regime was toppled but we didn't believe he had the capability to do anything in the UK," she said.
But MI5 "did not foresee" the number of Britons who became involved in extremist plots at home -- such as the July 7, 2005 bombings in London which killed 52 people -- following the conflict, she said.
"Our involvement in Iraq radicalised, for want of a better word, a whole generation of young people -- not a whole generation, a few among a generation -- who saw our involvement in Iraq and Afghanistan as being an attack on Islam," she said.
"During 2003-04, we realised that the focus was not foreigners. The rising and increasing threat was a threat from British citizens and that was a very different scenario to, as it were, stopping people coming in."
Manningham-Buller also said there was "no credible intelligence" linking Iraq to the September 11 attacks in the US.
"There is no credible intelligence to suggest that connection. That was the judgment of the CIA. It was not a judgement that found favour in some parts of the American machine," she said.
The probe is due to report by the end of the year and will hear from former UN weapons inspector Hans Blix as well as senior military figures next week.