The quick answer is that my role is to give the Prime Minister advice on who goes into deputy minister roles and to give the Prime Minister advice on machinery of government, such as how decision-making processes can be organized, the creation of cabinet committees and working groups, that sort of thing, and how departments can be structured.
Successive governments have pulled apart and put together government departments and agencies in different combinations as they adapt to a changing world. There's a long history of that. Those are prerogatives of the Prime Minister, and the advice on who to put into deputy minister roles comes from me. I'm accountable for it, or answerable for it, and the advice on machinery of government comes from me through the Privy Council. After that, it is up to each minister to be answerable to Parliament and up to each deputy minister to be answerable for their responsibilities as the accounting officer, which I know you've had time to talk about at this committee.