In the early 20th century, when travel by ship was still the norm, it was not uncommon for there to be an acting prime minister for months on end.
[1] An acting prime minister is required quite frequently – for instance, between 3 December 2007 and 23 February 2009 (during Kevin Rudd's first term), Julia Gillard acted as prime minister on 16 separate occasions.
[citation needed] In February 1958, Prime Minister John Diefenbaker appointed Ellen Fairclough as acting prime minister for two days while he was absent from his duties; Fairclough was historically noteworthy as the first woman ever given the duty.
[5] Whilst in other countries the term "Acting Prime Minister" only refers to an individual actually performing the role, in Israel the term is also in use when a designated Minister is allocated, even if they never actually perform the role.
In New Zealand, the acting prime minister is the designated head of government when the incumbent is not available to fulfill their duties.
Wijeyananda Dahanayake was appointed acting prime minister on September 26, 1959 following the assassination of S. W. R. D. Bandaranaike.
According to Rodney Brazier, there are no procedures within government to cope with the sudden death of the prime minister.
[16] Despite refusing "...to discuss a hypothetical situation" with BBC News in 2011,[17] the Cabinet Office is said to have said in 2006:[18]There is no single protocol setting out all of the possible implications.
The King would probably be looking for a very senior member of the Government (not necessarily a Commons Minister since this would be a short-term appointment).
If there was a recognized deputy to the Prime Minister, used to acting on his behalf in his absences, this could be an important factor.