We have before excused public servants from answering questions that relate to their relationship with their ministers.
On page 1068 in chapter 20 it says:
Particular attention is paid to the questioning of public servants. The obligation of a witness to answer all questions put by the committee must be balanced against the role that public servants play in providing confidential advice to their Ministers. The role of the public servant has traditionally been used in relation to the implementation and administration of government policy, rather than the determination of what that policy should be. Consequently, public servants have been excused from commenting on the policy decisions made by the government.
Essentially, we aren't expecting you to answer what ministers or the Prime Minister did or said, or what they didn't say. So I'll just put that out there and then ask you to answer.