the department. In that respect a PS and APS will often be in a position of debate with colleagues of much higher seniority, as well as be a sounding board for senior officials in the department and other ministerial private offices in Whitehall. A PS or an APS is always in attendance with the minister at every official meeting or event to provide support; and to ensure that a member of the Civil Service, who are non-political appointees, takes a factual note of discussions and commitments made. They also have ownership of the ministerial diary, managing the minister's time with the diary secretary. This means prioritising invitations, commitments, policy briefings and submissions and parliamentary business. A PS is always the initial source of advice to Ministers on policy, parliamentary protocol, the process of cabinet government and departmental administration. Often the PS and APS will take on specific responsibilities within the private office, dividing their minister's portfolio between them, with each PS dealing solely with policy, correspondence and diary matters relating to it. They often deputise and support other members of the PO temporarily, but would be considered subject matter experts for that area of work in the department. Working in a private office as a private secretary or an assistant private secretary is highly desired due to widely being seen as essential for advancement to the Senior Civil Service. Although considered to be a highly rewarding and sought-after post, it is one of the most difficult when compared to others at the equivalent grade. Depending upon the seniority of their political principal, private secretaries may be regarded as important officials in their own right; the Principal Private Secretary to the Prime Minister being the most important and is currently equivalent to a Director General in the Civil Service. Other notable positions include the Principal Private Secretary to the Secretary of State for Foreign and Commonwealth Affairs and the Private Secretary for Foreign Affairs to the Prime Minister. A Parliamentary Private Secretary (PPS) is a member of Parliament appointed to act as unpaid assistant to a minister, and should not be confused with a private secretary. The Sovereign and other royal households The Private Secretary to the Sovereign is viewed as being equivalent to a Permanent Secretary, the head of a government department. Private secretaries also work in the royal households for the other working members of the British royal family.