The headline is that Tony Blair admits to lying to the British people on the invasion of Iraq. The body of the article gives a slightly different impression. The lie is not about the existence of WMD--he apparently believed that they were there--but that he would have wanted to have Sadamn out even without the WMD issue. Why is this misleading? Because in a speech running up to the war he said, "I don't think any member of this house wants war." You see? He said that he didn't want war but in fact he did want war.
First, it is no contradiction to not want war and to want Sadamn's murderous regime out. I don't want to gain weight. I also don't want to give up scotch and cheese cake. The question is which one I don't want more.
But the more important point is the distortion of our view caused by the influence of legal thought on view of the world. What he has admitted is, from the policy point of view, hardly embarrassing at all. In addition to the 'legal' reasons for the Iraq invasion he had other reasons for it--chief among them that Sadamn was a genocidal murderer. Additional reasons for doing something do not, in themselves, undermine other reasons for doing something. Finding additional reasons for doing something is more justification for a policy, not less.
It is only when viewed through the legal worldview that all of the other reasons for invading Iraq are a liability. Viewed through the legal framework they are prejudicial; the US and Great Britain were not neutral and impartial towards the Iraqi regime and therefore the later judgment that it had to go was tainted.
So, the importance of the revelations in the article, if such they can be called, are entirely a function of whether or not one adopts the legalistic view of foreign policy.