Totally agree. I can't excuse Iraq, but it's a shame that's all Blair will be remembered for. I think he started out with good intewntions, but got corrupted by power - like so many before him.
I think he got caught up with the whole WMD thing and didn't listen to his advisers or the ballistics experts. Who were telling him that there were no WMD's. There was the whole 'sexed up' dossier which was clearly compiled by hawks who wanted regime change, which I think Blair wanted too, as he probably thought that getting rid of Saddam Hussien was a good thing (he was a brutal dictator). Then as mentioned, he'd handcuffed himself to Bush by giving him an assurance that 'come what may, the UK will back the US in Iraq'. He basically snookered himself and then couldn't back down.
In hindsight, a massive mistake with horrendous consequences that has made the middle east far more volatile that it ever was (in recent history anyway) But on the domestic front, Blair actually did a good job as PM.
