In british law, the "Will of Parliament" is the cornerstone of the british legal system and constitution.

No parliament may bind another ie, no parliament may legislate to undermine it's own absolute supremacy constitutinally nor that of any future, as yet unelected parliament.

The executive already has the privilege of taking us to war, keeping secrets and intervening in specific cases where it deems itself justified to do so.

The courts decide on the legality of decisions made by the executive. If a decision is contrary to the will of parliament then they will view it as illegal.

Likewise they will not ratiify any decision that they view as undermining the supremacy of parliament, as it would be a constitutional fallacy to argue that parliament would try to undermine itself.

That is the bedrock of democracy in the UK. The courts will always be loyal to the will of parliament and will not waste time fannying around with paradox's regarding parliaments that undermine themselves.

Therefore, if the executive acts in a way that undermines the will of parliament, whether they have persuaded Parliament to give them that power or not, the courts will ultimately view their action as illegal and they may be held accountable, as no parliament has the power to give the executive that right.

What aspect of this bill changes that reality?

I think this is the great strength of the British constitution, is that can survive pruning and savaging without suffering extensive damage. It absorbs change and evolves. It is inexhaustively deep and tony blair is but a pebble sinking through the darkness.

(PS, this is not my point of view, it is the reality of British law. To understand it, you need to learn the subject and see how it has worked in the past.

It's not so much an explanation of a philosophical idea as a description of a mechanism - like how a car works.