On 17 January 1710 Pratt was assigned, with Sir Simon Harcourt, as counsel for Henry Sacheverell, but declined to act. On 20 December 1711 he appeared before the House of Lords in support of the patent conferring an English dukedom on James Douglas, 4th Duke of Hamilton. On 28 December 1711 he was returned to parliament for Midhurst, for which he sat a silent (or all but) member until the dissolution which followed the accession of George I. Meanwhile, on Lord Cowper's recommendation, he was raised to a puisne judgeship in the court of king's bench, and was sworn in accordingly on 22 November 1714 and knighted.