By Nick Assinder BBC News Online political correspondent

Last week it was the passionate Blair - full of warnings that our children would never forgive us if we let Saddam Hussein off the hook today.

On Tuesday it was the cool, reasoning Blair, seeking to persuade us that, not only was the process of tackling Iraq right, but the only possible course of action.

This man knows precisely which tone to adopt for each audience

And his performance before the Commons liaison committee was all shirt sleeves, first names and inclusive smiles.

Anyone expecting a mauling or that the prime minister would, finally, be caught off balance would have been disappointed.

This man knows precisely which tone to adopt for each audience.

With the press he is presidential, sometimes challenging.

With Iain Duncan Smith he is dismissive and disbelieving. With these senior committee chairmen he was helpful and candid.

And in all three cases he is confident, self assured and self-believing.

Right

Much as it infuriates his critics, it is hugely difficult to trip him up, catch him out, or even - when all else fails - wind him up.

Mr Blair has honed his answers to the point he can roll them out in his sleep

So, when he insists he is standing by George Bush not because he is a supine poodle but because he absolutely believes he is right to do so, he clearly believes every word of it.

No one has yet found a way of introducing even a sliver of self-doubt into Tony Blair's psychology.

And no one watching his performance in front of the committee would have been left in any doubt that this is a man who is set on a course of action from which nothing will divert him.

Of course the senior parliamentarians were not going to start a shouting match with him.

They take their role very seriously and were there to calmly and carefully examine his policy on Iraq.

Serious

That may mean there was little in the way of fireworks, but it cannot be claimed they did not hold the prime minister to account.

And that was clearly a large part of his desire to carry out this exercise.

It is hard to think of a serious question that was not asked - and there were even one or two he had not faced before.

It probably didn't get us very far, however.

All these arguments have been extensively rehearsed and Mr Blair has honed his answers to the point he can roll them out in his sleep.

There is, however, one pretty substantial downside to all this self-confidence and authority.

Hint

It can look like intransigence or tunnel vision.

For example, his statement that there was "merit" in President Bush's plans for a Star Wars missile defence system involving Britain, sounded like a pretty big hint.

Opponents to the system had better brace themselves - it looks like the prime minister will take a fair bit of persuading not to back Bush on this one as well.

So, at the end of this session, not much had changed other than the prime minister had again shown his willingness to be cross examined over his policy.

He is unlikely to ask the Commons to vote for war before it happens - so these sorts of performances will have to pass for consultation instead.