Downing Street closely managed efforts to try to stabilise Iraq in the aftermath of the invasion of 2003, the inquiry into the conflict was told today.
Sir William Patey, who was British ambassador to Baghdad from 2005 to 2006, said that for the first time in his career he received instructions directly from the prime minister, Tony Blair.
Giving evidence on the first day of public hearings, he said throughout his time in the post he would receive almost daily telephone calls from No 10 urging him to take particular courses of action.
"The politics here demanded instant results," he told the inquiry.
"The first time I have ever had instructions as an ambassador directly from the prime minister was help get a constitution that the Iraqis would vote positively for, the formation of a new government, create the conditions for the withdrawal of British troops. It was quite simple."
He added: "They were quite reasonable instructions, provided you realised that they weren't in my gift or solely in the gift of the British Government.
"There was a tension between the desire for instant results and the realities on the ground. What you could achieve in the sort of timescales that London needed for political reasons - there was a disconnect."
Sir William said that, in particular, he had been under pressure from Downing Street to engage with the radical Shia cleric, Muqtada al Sadr, who was leading an insurgency against international coalition forces.
"There was rarely a day went by when I did not have a phone call from No 10," he said. "I was encouraged by No 10 to reach out to the Sadrists to give them the message that we felt they had a place in the political system."
He acknowledged however that his efforts had had only limited success.
"Moqtada refused to see me throughout my time there and every Sadrist I did see seemed to lose their job very soon afterwards," he said.
"They were very reluctant to engage with us but we tried to engage with them."
Overall he acknowledged that the British had struggled to influence events on the ground and to rebuild the shattered infrastructure in southern Iraq - the UK area of control.
"I think the level of ambition was probably higher than the ability to deliver. What could be delivered on powerpoint could not necessarily be delivered on earth," he said.
"There were formidable obstacles in terms of getting the power grid up, power stations built, oil pipelines repaired and I can't say we had a huge amount of success."Reuse content