I can't accept that interpretation, Archie.
I think Blair went into this (albeit with perhaps marginally-less enthusiasm), because he was prepared to support America in its endeavour, no matter what. Whilst it seems clear he made at least some attempt to modulate the gung-ho approach adopted by Bush, I think he basically folded his hand when it became clear that the US was going-in regardless.
The lack of appropriate consultation with Cabinet, and the sexing-up of the WMD dossier (abundantly clear from Chilcott that this is exactly what happened) to convince Parliament to support the War, all point to a guy who was prepared to either ignore or manipulate the evidence, to achieve his desired end. Supporting an American policy position seems to have had a greater bearing on him, than any other consideration.
Claiming he truly believed in the evidence, and had "best intentions" in mind, are not - in my view - sufficient mitigation for his actions. He ignored every note of caution that was presented to him, which makes him pretty-much solely accountable (as far as UK participation is concerned) for the way events played-out, and if we had any balls, we would give him up to the Hague. Instead, we let him ponce about the planet earning money hand-over-fist, as if he is some kind of indispensable, global Statesman.
It actually makes me want to puke.