Question: Which party did the English Prime Minister and subject of Barbara Learning lead from 1940 to 1955?

Context paragraphs:
Deputy Prime Minister of Pakistan: The office of the Deputy Prime Minister of Pakistan (Urdu: ‎ ) was created by the Prime Minister of Pakistan on 25 June 2012.  The main coalition party, Pakistan Muslim League (Q) (PML-Q), demanded to make a post of Deputy Prime Minister which was accomplished by the newly elected Prime Minister Raja Pervez Ashraf.  The main purpose of the post was to give a backup to the government in the absence of the Prime Minister.  As a result of an agreement between the ruling Pakistan Peoples Party (PPP) and the PML-Q to share ministries in the federal cabinet, Chaudhry Pervaiz Elahi was made the first Deputy Prime Minister of Pakistan.

Cook Islands First Party: The Cook Islands First Party (originally known as the Demo Tumu Party, translatable as "Original/True Democratic Party") was a political party in the Cook Islands.  The party was originally a faction within the Cook Islands Democratic Party which supported Prime Minister Robert Woonton over Terepai Maoate.  The 2004 elections saw the Democrats win a clear majority, but it was not clear whether Woonton would have the numbers within the party to remain Prime Minister.  Woonton's announcement on 15 November 2004 that he was forming a coalition with the rival Cook Islands Party with himself as Prime Minister.  This touched off a bitter struggle within the Democrats, which ultimately saw Woonton and his Health Minister Peri Vaevae Pare expelled from the party.  Woonton responded by launching his own party, the Demo Tumu Party, on 1 December 2004.

Winston Churchill: Sir Winston Leonard Spencer-Churchill, {'1': ", '2': ", '3': ", '4': "} (30 November 187424 January 1965) was a British statesman, army officer, and writer.  He served as Prime Minister of the United Kingdom from 1940 to 1945 and again from 1951 to 1955.  As a Member of Parliament (MP), he represented five constituencies over the course of his career.  As Prime Minister, Churchill led Britain to victory during World War II.  He led the Conservative Party for fifteen years from 1940 to 1955.

Deputy Prime Minister of Finland: The Deputy Prime Minister of Finland is a member of the Government who becomes the acting Prime Minister when the actual Prime Minister is temporarily unable to discharge his or her duties.  The Deputy Prime Minister is appointed by the Government and traditionally comes from the second largest party of a coalition government.  In recent years he/she has usually been Minister of Finance as well.  The current Deputy Prime Minister of Finland is Petteri Orpo, Minister of Finance.

Cabinet of Israel: The Government of Israel (officially: Hebrew: ממשלת ישראל‎ ‎ "Memshelet Yisrael") exercises executive authority in the State of Israel.  It consists of ministers who are chosen and led by the prime minister.  The composition of the government must be approved by a vote of confidence in the Knesset (the Israeli parliament).  Under Israeli law, the prime minister may dismiss members of the government, but must do so in writing, and new appointees must be approved by the Knesset.  Most ministers lead ministries, though some are ministers without portfolio.  Most ministers are members of the Knesset, though only the Prime Minister and the "designated acting prime minister" are required to be Knesset members.  Some ministers are also called deputy and vice prime ministers.  Unlike the designated acting prime minister, these roles have no statutory meanings.  The government operates in accordance with the Basic Law.  It meets on Sundays weekly in Jerusalem.  There may be additional meetings if circumstances require it.  The prime minister convenes these meetings.

Clement Attlee: Clement Richard Attlee, 1st Earl Attlee, {'1': ", '2': ", '3': ", '4': "} (3 January 1883 – 8 October 1967) was a British Labour politician who served as Prime Minister of the United Kingdom from 1945 to 1951 and Leader of the Labour Party from 1935 to 1955.  In 1940, Attlee took Labour into the wartime coalition government and served under Winston Churchill, becoming the first person to hold the office of Deputy Prime Minister of the United Kingdom.  He went on to lead the Labour Party to an unexpected landslide victory at the 1945 general election; forming the first Labour majority government, and a mandate to implement its postwar reforms.  The 12.0% national swing from the Conservatives to Labour was unprecedented at that time and remains the largest ever achieved by any party at a general election in British electoral history.  He was re-elected with a narrow majority at the 1950 general election.  In the following year, Attlee called a snap general election, hoping to increase his parliamentary majority.  However, he was narrowly defeated by the Conservatives under the leadership of Winston Churchill; despite winning the most votes of any political party in any general election in British political history until the Conservative Party's fourth consecutive victory in 1992.  Attlee remains the longest-ever serving Leader of the Labour Party.

Milady de Winter: Milady de Winter, often referred to as simply Milady, is a fictional character in the novel "The Three Musketeers" (1844) by Alexandre Dumas, père, set in 1625 France.  She is a spy for Cardinal Richelieu and is one of the dominant antagonists of the story.  Her role in the first part of the book is to seduce the English Prime Minister, the Duke of Buckingham, who is also the secret lover of Queen Anne of France.  Hoping to blackmail the Queen, Richelieu orders Milady to steal two diamonds from a set of matched studs given to Buckingham by the Queen, which were a gift to her from her husband, King Louis XIII.  Thwarted by d'Artagnan and the other musketeers, Milady's opposition of d'Artagnan carries much of the second half of the novel.

Han Myeong-sook: Han Myeong-sook (born March 24, 1944; Korean: 한명숙 ] ) was the Prime Minister of South Korea from April 2006 to March 2007.  She is South Korea's first female prime minister (second female prime minister overall if the acting premiership of Chang Sang is included).  She was from the United New Democratic Party (UNDP) as a member of the Korean National Assembly (representative) for Ilsan-gab, and is a graduate of Ewha Womans University in Seoul with a degree in French literature.  She resigned as Prime Minister on March 7, 2007 and declared her presidential candidacy.  But she did not succeed in the nominations.  In 2008 she ran for parliament, but was not elected.  However, in January 2012 she was elected leader of the main oppositional Democratic United Party (DUP) before the April legislative elections and became a member of parliament.  But the liberals did not manage to defeat the ruling Saenuri Party and Han stepped down as party leader in April 2012.  In August 2015, Han was convicted of receiving illegal donations at the amount of 900 million KRW, and sentence to two years in prison.  She is ineligible to run for public office for ten years after her prison term.  She became the first former prime minister of the Republic of Korea to serve a prison time.

Barbara Leaming: Barbara Leaming is a bestselling American biographer, whose subjects have included Roman Polanski, Orson Welles, Rita Hayworth, Marilyn Monroe, John F. Kennedy, Winston Churchill, and Jacqueline Kennedy Onassis.

Julia Gillard: Julia Eileen Gillard, {'1': ", '2': ", '3': ", '4': "} (born 29 September 1961) is a former Australian politician who was the 27th Prime Minister of Australia from 2010 to 2013, as Leader of the Australian Labor Party.  She was previously the 13th Deputy Prime Minister of Australia, and held the cabinet positions of Minister for Education, Minister for Employment and Workplace Relations and Minister for Social Inclusion from 2007 to 2010.  She was the first and to date only woman to hold the positions of deputy prime minister, prime minister and leader of a major party in Australia.

Supporting paragraphs: Barbara Leaming Winston Churchill
Answer: the Conservative Party