Sir Henry Campbell-Bannerman was a British statesman and Liberal politician who served as Prime Minister of the United Kingdom from 1905 to 1908 and Leader of the Liberal Party from 1899 to 1908. He also served as Secretary of State for War twice, in the cabinets of Gladstone and Rosebery. He was the first first lord of the treasury to be officially called the "prime minister", the term only coming into official usage five days after he took office. He remains the only person to date to hold the positions of Prime Minister and Father of the House at the same time, and the last Liberal leader to gain a UK parliamentary majority.

The Liberal Party was one of the two major political parties in the United Kingdom, along with the Conservative Party, in the 19th and early 20th centuries. Beginning as an alliance of Whigs, free trade-supporting Peelites, and reformist Radicals in the 1850s, by the end of the 19th century, it had formed four governments under William Gladstone. Despite being divided over the issue of Irish Home Rule, the party returned to government in 1905 and won a landslide victory in the 1906 general election.