Fair enough. Good answer.
In Canada the budget is prepared by the Department of Finance, whereas the estimates are prepared by the Treasury Board Secretariat. That's one of the reasons they've been difficult to align.
I believe in the United Kingdom those functions are conducted within the same agency. I wonder if you could comment a bit on the pros and cons of having the two separate organizations challenging each other and perhaps holding each other to account a bit, versus having consistency and alignment between the different parts of the process?