Parliamentary Private Secretary to the Prime Minister Bonar Law's Parliamentary Private Secretary, J.C.C. Davidson acted in effect as his Chief of Staff. Margaret Thatcher's downfall from the Conservative Party leadership in 1990 is attributed by many to the actions of her Parliamentary Private Secretary, Peter Morrison, in failing accurately to count votes amongst Conservative backbenchers. Some Parliamentary Private Secretaries to the Prime Minister go on to hold higher office; Lord Dunglass served as Parliamentary Private Secretary under Neville Chamberlain and later went on to serve as Prime Minister in his own right. There can be multiple Parliamentary Private Secretaries to the Prime Minister at a given time.
Acting prime minister Minister, served as Acting Prime Minister for six days, after Norman Kirk died in office in 1974. Deputy Prime Minister Winston Peters was serving as Acting Prime Minister as of 21 June 2018 until 2 August 2018, while Jacinda Ardern took maternity leave. Prior to the establishment of the Deputy Prime Minister role, a senior Minister would be appointed to act as Prime Minister when, for example, the incumbent was travelling overseas. In the current era, when both the Prime Minister and Deputy Prime Minister are unavailable, the next highest ranking minister who is available will be asked to act