A tricky area this. Can a top civil servant in the Cabinet Office tell the head of a department - the permanent secretary - what to do?
The answer is clearly "no" to judge from a hearing last week of the Public Accounts Committee.
Yet the Cabinet Office is supposed to be overseeing the Coalition's reforms of central government, including major IT-related changes. It has this mandate from Downing Street.
Can those changes happen if permanent secretaries are politely indifferent to the Cabinet Office's proposals - changes that are designed to save billions of pounds a year?
Those changes include eliminating duplicated activities, rationalising thousands of data centres, and simplifying working practices. Having 44,000 separate procurement organisations in the public sector buying the same or similar things - according to Nigel Smith, former head of the Office of Government Commerce - is an unjustifiable waste of public money.
At the PAC hearing last week Ian Watmore, the former Government CIO and now Chief Operating Officer at the Efficiency and Reform Group, Cabinet Office, confirmed to the committee chairman that his task is to eke out efficiencies.
The chairman, Margaret Hodge MP, asked Watmore a question that's arguably one of the most important in the debate over whether the public sector will make the savings required by the coalition.
She asked whether Watmore [as a top civil servant in the Cabinet Office] can ensure that the permanent secretary at the Home Office makes the savings required of him.
Watmore replied: "The day I tell David Normington what to do, could, I think, be an interesting day." Normingham is the permanent secretary at the Home Office [ who's retiring at the end of December].
Watmore said that if there appeared to be a spending anomaly, for good or bad reasons, he would "pick up the phone to David and talk to him about it".
But what if David says, "Leave me alone."?
Watmore: "Ultimately the expenditure that David has in the Home Office is for him as accounting officer and for the Home Secretary as Secretary of State to deal with, so we are not trying to blow their accountability; it is meant to be more helpful."
Watmore's frank reply is, perhaps, confirmation that the Cabinet Office has limited power over departments. So can it enforce the coalition's will when it comes to IT and other reforms of central government?
Normington seemed embarrassed at Watmore's powerlessness.
"No, I do not think I can say, "Leave me alone," said Normington. "I mean, sometimes you do that with the centre, but I do not think you can do that in this case, because the monitoring process is an escalating one which eventually gets to the Prime Minister.
"I will only say, 'Leave me alone,' if I know that I am on ground which justifies that. I think the process is one where if the problem continues it will be escalated and eventually - all of us will try to avoid this- we will be in front of the Prime Minister explaining why we have not done it."
But even if they come before the Prime Minister permanent secretaries have little to fear. In theory David Cameron can order them to make savings and changes they don't want to make. Unlikely in practice though.
Indeed Watmore hinted that systemic changes in the way government works are a long way off. He told the PAC:
The coalition's cuts are a chance to reform the way government works - to reduce its complexities at least. It would be a pity if little were to change."There are three types of change going on. There’s the change in head office land, which is here and now; there are changes in the big Government agencies, which are probably spread over the next couple of years; and then there are changes in the wider system, which are probably much longer term."