As it began, anti-war protesters gathered near the QEII venue across from the House of Commons. Three wore masks of George W Bush, Tony Blair and Gordon Brown with their hands and faces covered in fake blood.

The inquiry heard how prior to 9/11 the US administration had been adopting the same policy as the UK: seeking to contain Iraq through sanctions and the no-fly zones.

Sir Peter Ricketts, former chairman of the Joint Intelligence Committee, said Britain had favoured strengthened “smart sanctions”, a position initially backed by senior figures in the US administration.

However, he pointed out: “We were conscious there were other voices in Washington, some of whom were talking about regime change.”

Sir Peter cited an article written by Condoleezza Rice, the then National Security Adviser, in which she warned that nothing would change in Iraq until Saddam was gone.

Sir William Patey, a senior Foreign Office official, admitted British officials had discussed regime change but decided it had “no basis in law”. However, he said Whitehall was “aware of these drumbeats from Washington”.

At the same time, Sir Peter explained how there was concern within his committee that Saddam was continuing to try to acquire weapons of mass destruction.

“In 2001, we were seeing an acceleration of work on missile programmes, we saw increased Iraq efforts to secure material for the nuclear programme and we saw continuing interest in chemical weapons research and development.”

However, following 9/11, Sir Peter said opinion in America hardened.

“The tone of voice was more if there turns out to be any link between Saddam Hussein and Osama bin Laden, that is going to have major implications for Iraq and Saddam Hussein,” he noted.

Simon Webb, who was policy director at the Ministry of Defence, claimed the change in the US was “dramatic”.

He said: “The shift in thinking was to say that we cannot afford to wait for these threats to materialise. We must be ready to engage potential threats wherever they emerge.”

Sir Peter recalled how from November 2001 he heard talk in Washington of a “Phase 2” in the “war on terror”.

He suggested the attacks had the effect of making the Pentagon rather than the State Department the “dominant instrument” in American foreign policy.

He also said that while the attacks had raised the “salience and prominence” of counter-terrorism and the non-proliferation of WMD in Whitehall, they did not at that stage affect Britain’s policy on Iraq.

“We had heard these noises about regime change. They weren’t really impinging on the Whitehall policy debate at that point.”

Sir Peter said that if the 9/11 attacks had not happened, Britain would have continued to pursue its policy of strengthening sanctions through the United Nations Security Council.

“I’m pretty sure we would have stuck to our guns on the policy we had,” he added.

The inquiry continues today. Witnesses this week include Sir Jeremy Greenstock, former UK ambassador to the UN.

Widow asks public to back armed forces in funeral tribute

The widow of a bomb disposal expert killed in Afghanistan called on the British people to show more support for troops as she paid tribute to her “warrior” husband at his funeral.

Christina Schmid told a service in Truro Cathedral, Cornwall, that she hoped the death of Staff Sergeant Olaf Schmid, 30, would help “unite” civilians and troops. Mrs Schmid, 34, of Winchester, Hampshire, who has a five-year-old son, Laird, also called on world leaders to do more to protect soldiers.

Wearing her husband’s medals, she said: “In my eyes, my husband – my son’s father – was a warrior. Olaf and troops like him join to serve traditional warrior values, to passionately protect the country they love, its ideals and especially their families, communities and each other.

“In past conflicts, where there was an immediate threat to our shores and our existence, soldiers were never plagued with self-doubt about the value of their role in society, and people and their soldiers were once close in unity.

“We might disagree with a war; however, I hope Olaf’s death, my public storytelling and appreciation, and our community display of respect here can serve to bridge that gap and unite us once more with our troops.”

Mrs Schmid added: “From now, on I expect our peacemakers to show us they are working as hard as he did to preserve life.”