Namier used prosopography or collective biography of every Member of Parliament (MP) and peer who sat in the British Parliament in the latter 18th century to reveal that local interests, not national ones, often determined how parliamentarians voted. Namier argued very strongly that far from being tightly organised groups, both the Tories and Whigs were collections of ever-shifting and fluid small groups whose stances altered on an issue-by-issue basis. Namier felt that prosopographical methods were the best for analysing small groups like the House of Commons, but he was opposed to the application of prosopography to larger groups. At the time of its publication in 1929, "The Structure of Politics at the Accession of George III" caused a historiographical revolution in understanding the 18th century.