Question: Who was the oldest Prime Minister to pay homage at the funeral of Margaret Thatcher?

Context paragraphs:
Commonwealth Heads of Government Meeting 1986: The Commonwealth Heads of Government Meeting 1986 was the ninth Meeting of the Heads of Government of the Commonwealth of Nations.  It was held in London, the United Kingdom, between 3 August 1986 and 5 August 1986, and was hosted by that country's Prime Minister, Margaret Thatcher.  This was a special meeting held in between the biennial CHOGMs in order to consider the recommendations of the Commonwealth Eminent Persons Group regarding economic sanctions against South Africa due to its policies of apartheid.  British prime minister Margaret Thatcher's refusal to support mandatory sanctions resulted in an acrimonious meeting and almost led to a split in the Commonwealth.

Thatcher baronets: The Thatcher baronetcy, of Scotney in the County of Kent, is a Baronetcy created for the businessman Denis Thatcher on 7 December 1990 following the resignation of his wife, Conservative Prime Minister Margaret Thatcher, that year.  The current holder is Mark Thatcher, who succeeded his father in 2003.

James Callaghan: 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.

Swedish governmental line of succession: 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.

John Major: Sir John Major, {'1': ", '2': ", '3': ", '4': "} (born 29 March 1943) is a British politician who was Prime Minister of the United Kingdom and Leader of the Conservative Party from 1990 to 1997.  He served as Foreign Secretary and then Chancellor of the Exchequer in the Thatcher Government from 1989 to 1990, and was the Member of Parliament (MP) for Huntingdon from 1979 until he retired in 2001.  Since Margaret Thatcher's death in 2013, he is the oldest living former Prime Minister.

The Iron Lady (film): The Iron Lady is a 2011 British-French biographical drama film based on the life and career of Margaret Thatcher (1925–2013), a British stateswoman and politician who was the longest-serving Prime Minister of the United Kingdom of the 20th century.  The film was directed by Phyllida Lloyd.  Thatcher is portrayed primarily by Meryl Streep, and, in her formative and early political years, by Alexandra Roach.  Thatcher's husband, Denis Thatcher, is portrayed by Jim Broadbent, and by Harry Lloyd as the younger Denis.  Thatcher's longest-serving cabinet member and eventual deputy, Geoffrey Howe, is portrayed by Anthony Head.

University of Buckingham: The University of Buckingham (UB) is a non-profit, private university in the UK and the oldest of the country's five private universities.  It is located in Buckingham, England, and was founded as the University College at Buckingham (UCB) in 1973, admitting its first students in 1976.  It was granted university status by royal charter in 1983.  The university was closely linked to Margaret Thatcher, who as Education Secretary oversaw the creation of the university college in 1973, and as Prime Minister was instrumental in elevating it to a university in 1983 – thus creating the first private university in the UK.  When she retired from politics in 1992, Margaret Thatcher became the university's second chancellor, a post she held until 1998.

Nile Gardiner: Nile Gardiner is a British conservative commentator, director of the Margaret Thatcher Center for Freedom at The Heritage Foundation, and a former aide to British Prime Minister Margaret Thatcher.  He is also a commentator on U.S. and British television and a frequent contributor to the Fox News network, and the London "Daily Telegraph".  Gardiner is co-author with Stephen Thompson of the book, "Margaret Thatcher on Leadership: Lessons for American Conservatives Today" (Regnery 2013).

List of Prime Ministers of the United Kingdom: The Prime Minister of the United Kingdom is the head of the Government of the United Kingdom, and chairs Cabinet meetings.  There is no specific date when the office of Prime Minister first appeared, as the role was not created but rather evolved over a period of time.  The term was used in the House of Commons in 1805 and it was certainly in parliamentary use by the 1880s, and in 1905 the post of Prime Minister was officially given recognition in the order of precedence.  Modern historians generally consider Sir Robert Walpole, who led the government of Great Britain from 1721 to 1742, as the first Prime Minister.  Walpole is also the longest-serving Prime Minister by this definition.  However, Sir Henry Campbell-Bannerman was the first Prime Minister and Margaret Thatcher the longest-serving Prime Minister to have been officially referred to as such.

Death and funeral of Margaret Thatcher: Baroness Thatcher died of a stroke in London on 8 April 2013 at the age of 87.  On 17 April, the former Prime Minister was honoured with a ceremonial funeral.  Due to the polarised view of her achievements and legacy, reaction to her death was mixed throughout the United Kingdom, with her memory evoking both intense praise and criticism.  The funeral, including a formal procession through Central London, followed by a church service at St Paul's Cathedral, cost around £3.6 million including £3.1 million for security.  The funeral was notable for the attendance of Queen Elizabeth II.  All four of her successors as Prime Minister paid homage at the funeral.  Her body was cremated at Mortlake Crematorium following the funeral.

Supporting paragraphs: John Major Death and funeral of Margaret Thatcher
Answer: Sir John Major