Quote Originally Posted by Odin
How does this operate in the parlimentary system? Blair is the head of government by default of his majority. the majority votes to go to war so you now have a binding law? At that point who is in charge of its execution? (IE Commander in chief, please dont say its the monarch....).
Just to further illuminate what Pannonian has already written, the power to declare war is a royal prerogative - that is, a power retained by the monarch but invariably exercised by the Prime Minister (who supposedly shares the decision with Cabinet, but not necessarily in recent regimes). The Prime Minister is accountable to Parliament, but since by definition, he/she is the leader of the largest party, the PM can usually rely on their support. (To hold the PM accountable would, as Pannonian notes, lead to them putting their own seats at risk via the inevitable general election).

Tony Blair asking Parliament to support his action before taking it was a fairly major breach of convention. Oddly, he never actually needed to make up dossiers to convince MPs - he could just have gone ahead anyway.

In brief, for this and several other purposes, the Prime Minister of Great Britain has monarchial powers. They also own several kinds of fish.