William Pitt the Younger : Biographie, Réalisations et Héritage Durable

Pitt was regarded as an outstanding administrator who worked for efficiency and reform, bringing in a new generation of competent administrators. He increased taxes to pay for the great war against France and cracked down on radicalism. To counter the threat of Irish support for France, he engineered the Acts of Union 1800 and tried (but failed) to secure Catholic emancipation as part of the Union. He created the "new Toryism", which revived the Tory Party and enabled it to stay in power for the next quarter of a century.

The historian Asa Briggs argues that his personality did not endear itself to the British mind, for Pitt was too solitary and too colourless, and too often exuded an attitude of superiority. His greatness came in the war with France. Pitt reacted to become what Lord Minto called "the Atlas of our reeling globe". William Wilberforce said, "For personal purity, disinterestedness and love of this country, I have never known his equal." The historian Charles Petrie concludes that he was one of the greatest prime ministers "if on no other ground than that he enabled the country to pass from the old order to the new without any violent upheaval. ... He understood the new Britain." For this he is ranked highly amongst all British prime ministers in multiple surveys.

Pitt served as prime minister for eighteen years, 343 days, making him the second-longest-serving British prime minister. Having entered office at the age of 24, Pitt is the youngest prime minister in both British and world history.