Question: Who was prime minister of the UK from 1955  to 1957 that James Stuart served as Secretary of State for?
Context: The Swedish constitution of 1974 allows the Prime Minister of Sweden to appoint one of the Ministers in the cabinet as Deputy Prime Minister ("biträdande statsminister", also unofficially known as "vice statsminister", "Vice Prime Minister"), in case the Prime Minister for some reason is prevented from performing his or her duties.  However, if a Deputy Prime Minister has not been appointed, the Minister in the cabinet who has served the longest time (and if there are several with equal experience the one who is oldest) takes over as head of government.  Note that the person acting as Prime Minister does not do so on a permanent basis: if a Prime Minister dies, resigns or loses a vote of confidence in the Riksdag, the Speaker of the Riksdag will then confer with the parties of the Riksdag and propose a new Prime Minister, who must be tolerated by a majority of the Riksdag.  If the Prime Minister has resigned or lost a vote of confidence, he or she will remain the head of a government "ad interim" until the new Prime Minister assumes his or her office.  The only case where the governmental line of succession becomes relevant is when the Prime Minister dies (upon which the person next in the line of succession serves as the head of a government "ad interim") or when the Prime Minister is on leave or for any other reason incapable of serving, but still remains in office.  This might be compared to the Presidential line of succession in the United States, where the person next in line assumes the Presidency throughout the remainder of the term if the President dies, resigns or is impeached. The Chief Cabinet Secretary of Japan (内閣官房長官 , naikaku-kanbō-chōkan ) is a Minister of State who is responsible for directing the Cabinet Secretariat of Japan.  The main function of the Chief Cabinet Secretary is to coordinate the policies of ministries and agencies in the executive branch.  The Chief Cabinet Secretary serves as the government's press secretary, conducts policy research, prepares materials to be discussed at cabinet meetings, and, in time of national crisis, coordinates ministries and agencies of the executive branch.  The Chief Cabinet Secretary is customarily nominated as the first in line to serve as temporary Acting Prime Minister in case the Prime Minister is unable to serve due to death or other grave reasons until a new Prime Minister is appointed.  The Chief Cabinet Secretary's office is located on the fifth floor of the Prime Minister's official residence in Tokyo. Robert Anthony Eden, 1st Earl of Avon, (12 June 1897 – 14 January 1977) was a British Conservative politician who served three periods as Foreign Secretary and then a relatively brief term as Prime Minister of the United Kingdom from 1955 to 1957. Alexander Hugh Holmes Stuart (April 2, 1807 – February 13, 1891) was a prominent Virginia lawyer and American political figure associated with several political parties.  Stuart served in both houses of the Virginia General Assembly (1836-1838, 1857-1861 and 1874-1877), as a U.S. Congressman (1841-1843), and as the Secretary of the Interior (1850 - 1853).  Despite opposing Virginia's secession and holding no office after finishing his term in the Virginia Senate during the American Civil War, after the war he was denied a seat in Congress.  Stuart led the Committee of Nine which attempted to ameliorate Congressional Reconstruction, and also served as rector of the University of Virginia. Sanjaya Baru is a political commentator and policy analyst, currently serving as Director for Geo-Economics and Strategy at the International Institute of Strategic Studies.  Penguin India.  Retrieved on 14 April 2014. </ref> Previously he had served as associate editor at "The Economic Times" and "The Times of India", and then chief editor at "Business Standard".  His father B. P. R. Vithal served as Finance and Planning Secretary during former Prime Minister Manmohan Singh's stint as Secretary of Finance.  Before he became a journalist, he was a member of Communist Party of India (Marxist) when he was a student at University of Hyderabad.  He became Manmohan Singh's media advisor and chief spokesperson, a role in which he served from May 2004 until August 2008.  In April 2014, Penguin India published "The Accidental Prime Minister", Baru's tell-all memoir about his time at the Prime Minister's Office (PMO).  In it, Baru alleges that the prime minister was completely subservient to Congress President Sonia Gandhi, who wielded significant influence in the running of the Singh administration, including the PMO itself.  The book has sparked off a controversy, with the PMO officially denouncing it as "fiction".  Baru, however, has said that he set out to show an empathetic portrait of the prime minister. Sir Harold Arthur Stuart (29 July 1860 – 1 March 1923) was an Indian Civil Servant, the first Director of the Central Criminal Intelligence Department of India, and later a Home Secretary to the Government of India.  A graduate of King's College Cambridge, Harold Stuart was born in the city of York to Peter Stuart.  He entered the Indian Civil Service in 1881, serving as the Under Secretary to the Government of Madras.  From April 1904 till 1909, Stuart served as the head of the newly formed department of Criminal Intelligence, later serving as the Home Secretary to the Government of India and subsequently in the Executive Council. Leonard James Callaghan, Baron Callaghan of Cardiff, {'1': ", '2': ", '3': ", '4': "} (27 March 1912 – 26 March 2005), often known as Jim Callaghan, was a British politician who served as Prime Minister of the United Kingdom from 1976 to 1979 and Leader of the Labour Party from 1976 to 1980.  Callaghan is to date, the only British politician in history to have served in all four of the "Great Offices of State", having been Chancellor of the Exchequer from 1964–67, Home Secretary from 1967-70, and Foreign Secretary from 1974, until his appointment as Prime Minister in 1976.  As Prime Minister, he had some successes, but is mainly remembered for the "Winter of Discontent" of 1978–79.  During a very cold winter, his battle with trade unions led to massive strikes that seriously inconvenienced the public, leading to his defeat in the polls by Conservative leader Margaret Thatcher. David Stuart was the Ambassador of Australia to Austria from 2012 to 2016.  Prior, he was the Deputy Chief of Mission at the Embassy of Australia in Washington, D.C., between 2007 and 2010.  Stuart was appointed to the position in July 2007.  Before his role as Deputy Chief of Mission, Stuart served in the Department of Foreign Affairs and Trade (1981), was the Third Secretary at the Embassy of Australia in Madrid (1981–1984), a member of the Australian delegation to the United Nations Human Rights Council (1988–1992), Counsellor for Political Affairs at the Embassy of Australia in Jakarta (1997–1999), Australian ambassador and Deputy Permanent Representative to the United Nations (1999–2002), and the First Assistant Secretary at the International Security Division in Canberra. The Prime Minister's Department (Malay: "Jabatan Perdana Menteri" , abbreviated JPM) is a federal government ministry in Malaysia.  Its objective is "determining the services of all divisions are implemented according to policy, legislation / regulations and current guidelines".  It is headed by the Prime Minister of Malaysia followed by other Minister in the Prime Minister's Department.  The Department consists of the Prime Minister's Office, the Deputy Prime Minister's Office and more than 50 other government agencies and entities.  The Prime Minister's Department was established in July 1957.  Its headquarters are in Perdana Putra, Putrajaya. Captain James Gray Stuart, 1st Viscount Stuart of Findhorn, (9 February 1897 – 20 February 1971), styled The Honourable James Stuart between 1909 and 1957, was a Scottish Unionist politician.  He was joint-Parliamentary Secretary to the Treasury in Winston Churchill's war-time coalition government and later served as Secretary of State for Scotland under Churchill and then Sir Anthony Eden from 1951 to 1957.  The latter year he was elevated to the peerage as Viscount Stuart of Findhorn.
Answer: Anthony Eden