British officials secretly discussed the prospects for "regime change" in Iraq in late 2001 - more than a year before the invasion - the official inquiry into the war was told today.
On the first day of public hearings in London, the inquiry, headed by John Chilcot, heard that Foreign and Commonwealth Office (FCO) officials drew up an internal "options" paper which included the possibility of ousting Saddam Hussein.
However William Patey, the then head of the FCO's Middle East department, said the idea had been swiftly rejected on the grounds that there was "no basis in law" for such action.
The inquiry, which took evidence from a series of senior FCO and Ministry of Defence officials, heard that a two-page paper was drawn up against a background of growing impatience in the United States with the strategy of "containment" of Saddam.
The international sanctions regime was "in trouble", while there were increasing concerns that Saddam was making progress in his efforts to acquire weapons of mass destruction (WMD).
"This is a paper I commissioned from my staff and said 'Come on, let's have the whole range of options out here. Nothing's off the table'," Patey said.
The options went from "'hard' containment to 'soft' containment, to the lifting of sanctions, to - I have to say - we had at the end the regime-change option, which was dismissed at the time as having no basis in law."
He added: "It was very much an internal paper. We didn't go into how to achieve regime change."
However the inquiry heard that even in early 2001, elements of the new US administration of President George Bush were already discussing the possibility of "regime change" in Iraq.
Peter Ricketts, who was chairman of the Joint Intelligence Committee (JIC), said Britain wanted a strengthened "smart sanctions regime" - a position initially backed by senior figures in the Bush administration like US Secretary of State Colin Powell.
They were aware, however, of other influential figures in Washington who were already taking a harder line.
"We were conscious that there were other voices in Washington, some of whom were talking about regime change," he said.
He cited an article by then National Security Adviser Condoleezza Rice - written before Mr Bush actually took office - warning that "nothing will change" in Iraq until Saddam was gone.
Patey added: "We were aware of these drum beats from Washington and internally we discussed it. Our policy was to stay away from that end of the spectrum."
At the same time, Ricketts said there was concern within the JIC that Saddam was continuing in his efforts to acquire weapons of mass destruction (WMD).
"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 CW (chemical weapons) research and development," he said.
Following the 9/11 attacks on the Twin Towers in New York and the Pentagon in Washington, Ricketts said there had been a further hardening of opinion in the US.
"We heard people in Washington thought there might be some link between Saddam Hussein and Osama bin Laden - undocumented. I don't think we saw any evidence of it," he said.
"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."
Simon Webb, who was policy director at the Ministry of Defence, said he found that change in the US following the attacks was "dramatic".
"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," he said.
While the initial response concentrated on Afghanistan - where the 9/11 attacks had originated - Sir Peter said that, from November 2001, he began to hear talk in Washington of a "phase 2" in the "war on terror".
He said the attacks also had the effect of making the Pentagon rather than the State Department the "dominant instrument" in American foreign policy.
Mr Webb said that while there was no immediate change of policy in Washington to support regime change, that was where the policy debate was heading.
"The focus didn't shift to regime change. It shifted to the weapons of mass destruction problem which, in the case of Iraq, in order to deal with the weapons of mass destruction problem, you would probably end up having to push Saddam Hussein out of power," he said.
Ricketts 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 still had our focus on the weapons inspector route and the sanctions-type route. We had heard these noises about regime change. They weren't really impinging on the Whitehall policy debate at that point," he said.
He said that if the 9/11 attacks had not happened, he believed that Britain would have continued to pursue its policy of strengthening sanctions through the UN Security Council.
"I'm pretty sure we would have stuck to our guns on the policy we had," he said.
The inquiry was adjourned until tomorrow.