Anil Roberts is trying to save his job which is threatened, and his reputation is in tatters. He has referred to some questionable constitutional doctrines about the relationship between ministers and senior public servants.
If anything, ministerial responsibility is one of the classic conventions which derive from the Crichel Down case in which Sir Thomas Dugdale, a UK cabinet minister, resigned and took responsibility for acts of mismanagement and misgovernance in his ministry, even though he was not personally involved.
I am not sure what we believe in these days, but Mr Roberts has no wiggle room if we still subscribe to the Westminster convention of ministerial responsibility.
He has to go.