John Sadleir was an Irish financier and politician, who became notorious as a political turncoat, and committed suicide after the failure of his financial speculations. He served as the model for several fictional portrayals of speculators who come to ruin.

After the collapse of Lord Derby's minority government, the Whigs and Peelites formed a coalition under the Peelite leader Lord Aberdeen. The government resigned in early 1855 after a large parliamentary majority voted for a select committee to enquire into the incompetent management of the Crimean War. The former Home Secretary, Lord Palmerston, then formed his first government.