George Hamilton-Gordon, 4th Earl of Aberdeen,, styled Lord Haddo from 1791 to 1801, was a British statesman, diplomat and landowner, successively a Tory, Conservative and Peelite politician and specialist in foreign affairs. He served as Prime Minister from 1852 until 1855 in a coalition between the Whigs and Peelites, with Radical and Irish support. The Aberdeen ministry was filled with powerful and talented politicians, whom Aberdeen was largely unable to control and direct. Despite his trying to avoid this happening, it took Britain into the Crimean War, and fell when its conduct became unpopular, after which Aberdeen retired from politics.

The Peelites were a breakaway political faction of the British Conservative Party from 1846 to 1859. Initially led by Robert Peel, the former Prime Minister and Conservative Party leader in 1846, the Peelites supported free trade whilst the bulk of the Conservative Party remained protectionist. The Peelites later merged with the Whigs and Radicals to form the Liberal Party in 1859.