Admiral Lord Boyce, the then Chief of the Defence Staff, said he was only allowed by ministers to start full-scale planning four months before the invasion - far less time than they really needed.

He confirmed that the timelines were so tight, the 7th Armoured Brigade "Desert Rats" - the lead British formation - did not achieve full operational capability until the day before British and US troops went into Iraq on March 20 2003.

Lord Boyce also described how he had demanded assurances from Prime Minister Tony Blair that the military action was legal.

And he was scathing about the lack of preparations for dealing with post war Iraq both by the Department for International Development and the Americans.

Lord Boyce said that at the time of the 9/11 attacks in 2001 there had been "absolutely no contingency planning" by the British for military action against Iraq.

Preparations within the Ministry of Defence (MoD) were "ramped up" after Mr Blair visited president George Bush at his Texas ranch in April 2002, although they were restricted to a small group of senior officers.

Lord Boyce said ministers had been concerned that details would leak out, undermining their efforts to get a new United Nations Security Council resolution requiring Saddam Hussein to give up his weapons of mass destruction.

The issue was considered so sensitive that Lord Boyce said he was even ordered by the then Defence Secretary, Geoff Hoon, not to discuss it with the chief of defence logistics.

"I was prevented from doing that by the Secretary of State for Defence because of the concern of it becoming public knowledge that we were planning for a military contribution which might be unhelpful in the activity in the UN to secure a Security Council resolution," he said.

As a result, the military chiefs were unable to take any practical steps to prepare for military action, such as buying in the extra equipment they would need for the operation.

"All you would be doing was high level planning, saying this is what we could do when we got the go ahead to start bringing in people like the Defence Logistics Organisation," Lord Boyce said.

The MoD was only finally given the authorisation to begin "overt" planning in November 2002, following the passing of Security Council resolution 1441 requiring Saddam to disarm.

"The late stage at which I was finally given authority to start mobilising the logistics organisation to get the equipment that we needed left us with some very short timelines," he said.

In the end, he said that he was confident that the troops who were at "the front of the frontline" had the equipment they needed when the invasion began.

But pressed about the concerns raised by families of some the soldiers killed in action, he said: "I'm not familiar with the detail about things such as body armour. The unfortunate thing about going to war is that some people are going to get killed."

Lord Boyce said he had made clear to Mr Blair as early as January 2002 that he would need proper legal authorisation if he was to commit British forces to an invasion.

Eventually he was given a certificate by the Attorney General, Lord Goldsmith, although he indicated that he would have preferred a second Security Council resolution authorising military action which would have "completely nailed" it.

"Obviously the propriety or legality of what we were about to do was obviously a concern of mine - not least because, somewhat against my instincts, we had signed up to the ICC (International Criminal Court)," he said.

"I always made perfectly clear to the Prime Minister face-to-face - and indeed to the Cabinet - that if we decided to go into Iraq we would have to have a good legal basis for doing so, which obviously a second resolution would have completely nailed."