Question: What actor played Botswana's first president in A United Kingdom?

Context paragraphs:
Jefferson Memorial: The Jefferson Memorial is a presidential memorial in Washington, D.C., dedicated to Thomas Jefferson (1743–1826), one of the most important of the American Founding Fathers as the main drafter and writer of the Declaration of Independence, member of the Continental Congress, governor of the newly independent Commonwealth of Virginia, American minister to King Louis XVI and the Kingdom of France, first U.S. Secretary of State under the first President George Washington, the second Vice President of the United States under second President John Adams, and also the third President (1801–1809), as well as being the founder of the University of Virginia at Charlottesville, Virginia.

A United Kingdom: A United Kingdom is a 2016 British biographical romantic drama film directed by Amma Asante and written by Guy Hibbert, based on the true-life romance between Sir Seretse Khama and his wife Ruth Williams Khama.  David Oyelowo and Rosamund Pike portray Seretse and Ruth, respectively.

Abel Alier: Abel Alier Kwai (born 1933) is a South Sudanese politician and judge who served as Vice President of Sudan between 1971 and 1982 and as President of the High Executive Council of the Southern Sudan Autonomous Region between 1972 and 1978.  After Sudan gained independence from the United Kingdom in 1956, Southern Sudan was not left as an independent state.  This led to a deadly war a year before the independence.  A party in the war was Anyanya 1 Under Joseph Lagu.  Abel Alier was a politician who managed to complete his college education among many Southern Sudanese.  He is an internationally respected judge, human-rights lawyer and activist on behalf of Christians in the Sudan.  Former Vice President of Sudan (1971–1982), he served as the first president of the High Executive Council of Southern Sudan.  He sits on the Permanent Court of International Arbitration in The Hague and is recognized as Sudan's most prominent Christian lawyer.  His latest book is "Southern Sudan: Too Many Agreements Dishonoured".

Janet Banana: Janet Banana (born Janet Mbuyazwe) in 1938 in Matabeleland) is the widow of Zimbabwe's first President, the late Canaan Banana, whom she married in 1961.  She served as the first First Lady of Zimbabwe from 1980 to 1987.  The couple had four children.  Mrs. Banana sought political asylum in the United Kingdom in October 2000.  She was awarded British citizenship in 2006, and took the oath of allegiance on 10 February 2006 in a ceremony in the London Borough of Haringey in front of the Mayor of Haringey.

Scottish Labour Party (1888): The Scottish Labour Party (SLP), also known as the Scottish Parliamentary Labour Party, was formed by Robert Bontine Cunninghame Graham, the first socialist MP in the parliament of the United Kingdom, who later went on to become the first president of the Scottish National Party, and Keir Hardie, who later became the first leader of the British Labour Party.

Clay Mathematics Institute: The Clay Mathematics Institute (CMI) is a private, non-profit foundation, based in Peterborough, New Hampshire, United States.  CMI's scientific activities are managed from the President's office in Oxford, United Kingdom.  The institute is "dedicated to increasing and disseminating mathematical knowledge."  It gives out various awards and sponsorships to promising mathematicians.  The institute was founded in 1998 through the sponsorship of Boston businessman Landon T. Clay.  Harvard mathematician Arthur Jaffe was the first president of CMI.

Victorian painting: Victorian painting refers to the distinctive styles of painting in the United Kingdom during the reign of Queen Victoria (1837–1901).  Victoria's early reign was characterised by rapid industrial development and social and political change, which made the United Kingdom one of the most powerful and advanced nations in the world.  Painting in the early years of her reign was dominated by the Royal Academy of Arts and by the theories of its first president, Joshua Reynolds.  Reynolds and the academy were strongly influenced by the Italian Renaissance painter Raphael, and believed that it was the role of an artist to make the subject of their work appear as noble and idealised as possible.  This had proved a successful approach for artists in the pre-industrial period, where the main subjects of artistic commissions were portraits of the nobility and military and historical scenes.  By the time of Victoria's accession to the throne this approach was coming to be seen as stale and outdated.  The rise of the wealthy middle class had changed the art market, and a generation who had grown up in an industrial age believed in the importance of accuracy and attention to detail, and that the role of art was to reflect the world, not to idealise it.

Robert Bontine Cunninghame Graham: Robert Bontine Cunninghame Graham (24 May 1852 – 20 March 1936) was a Scottish politician, writer, journalist and adventurer.  He was a Liberal Party Member of Parliament (MP); the first ever socialist member of the Parliament of the United Kingdom; a founder, and the first president, of the Scottish Labour Party; a founder of the National Party of Scotland in 1928; and the first president of the Scottish National Party in 1934.

Sam Nujoma: Samuel Daniel "Shafiishuna" Nujoma, ( ; born 12 May 1929) is a Namibian revolutionary, anti-apartheid activist and politician who served three terms as the first President of Namibia, from 1990 to 2005.  Nujoma was a founding member and the first president of the South West Africa People's Organization (SWAPO) in 1960.  He played an important role as leader of the national liberation movement in campaigning for Namibia's independence from South African rule.  He established the People's Liberation Army of Namibia (PLAN) in 1962 and launched a guerrilla war against the apartheid government of South Africa in 1966, beginning after the United Nations withdrew the mandate for South Africa to govern the territory.  Nujoma led SWAPO during the lengthy Namibian War of Independence, which lasted from 1966 to 1989.

Ruth Williams Khama: Ruth Williams Khama, Lady Khama (9 December 1923 – 22 May 2002) was the wife of Botswana's first president Sir Seretse Khama, the Paramount Chief of its Bamangwato tribe.  She served as the inaugural First Lady of Botswana from 1966 to 1980.

Supporting paragraphs: A United Kingdom Ruth Williams Khama
Answer: David Oyelowo