Question: Who was Britain's oldest Prime Minister and lived in the Seaforth House built for his father? 
Context: The Prime Minister of Canada is an official who serves as the primary minister of the Crown, chair of the Cabinet, and thus head of government of Canada.  Officially, the prime minister is appointed by the Governor General of Canada, but by constitutional convention, the prime minister must have the confidence of the elected House of Commons.  Normally, this is the leader of the party caucus with the greatest number of seats in the house.  But, if that leader lacks support of the majority, the governor general can appoint another leader who has that support or may dissolve parliament and call a new election.  By constitutional convention, a prime minister holds a seat in parliament and, since the early 20th century, this has more specifically meant the House of Commons. William Ewart Gladstone, ( ; 29 December 1809 – 19 May 1898) was a British Liberal statesman and earlier Conservative politician.  In a career lasting over 60 years, he served as Prime Minister four separate times (1868–74, 1880–85, February–July 1886 and 1892–94), more than any other person, and served as Chancellor of the Exchequer four times.  Gladstone was also Britain's oldest Prime Minister; he resigned for the final time when he was 84 years old. Frank Fletcher Hamilton (3 April 1921 – 1 February 2008) was a Progressive Conservative member of the House of Commons through 4 separate successful elections (1972–1984).  He represented the federal riding of Swift Current—Maple Creek, Saskatchewan.  Liberal Prime Minister Pierre Trudeau led a minority.  The 29th Canadian Parliament was in session from 4 January 1973 until 9 May 1974.  The 30th Canadian Parliament was in session from 30 September 1974 until 26 March 1979.  The 31st Canadian Parliament was a briefly lived parliament in session from 9 October until 14 December 1979 under the leadership of a Progressive Conservative minority and Prime Minister Joe Clark.  The 32nd Canadian Parliament was in session from 14 April 1980 until 9 July 1984 and was controlled by a Liberal Party majority, led first by Prime Minister Pierre Trudeau and the 22nd Canadian Ministry, and then by Prime Minister John Turner. 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. Sri Temasek is a two-storey detached house built in 1869 which is sited within the grounds of the Istana in Singapore.  During the island's colonial era, it served as the residence of the Colonial Secretary or Chief Secretary.  Since the establishment of the State of Singapore in 1959, it has been the official residence of the Prime Minister of Singapore, though none of Singapore's Prime Ministers has ever lived there.  Together with the Istana, it was gazetted a national monument on 14 February 1992. The Swedish constitution allows the Prime Minister to appoint one of the Ministers in the cabinet as Deputy Prime Minister ("statsministers ställföreträdare", sometimes unofficially known as "vice statsminister"), 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 (these are marked in "italic" in the table below). Seaforth House was a mansion in Seaforth, Merseyside England built in 1813 for Sir John Gladstone, father of William Ewart Gladstone who was Prime Minister of the United Kingdom four times. 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. Josip Manolić (] ; born 22 March 1920) is a Croatian politician and former high-ranking official of the State Security Administration (UDBA or UDSA) who was the Prime Minister of Croatia from 24 August 1990 to 17 July 1991.  Croatia formally declared independence during his term, on 25 June 1991.  Having taken office as Prime Minister at the age of 70 and having left the office at the age of 71, he is the oldest person to date to have served as Prime Minister of Croatia.  Manolić is also the oldest currently living former prime minister at the age of and the longest-lived holder of the office.  Following his brief term as Prime Minister he served as the first Speaker of the Chamber of Counties, the upper house of the Croatian Parliament, from 1993 until 1994. 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.
Answer: William Ewart Gladstone