In 1836, Windthorst settled down as an advocate in Osnabrück: his abilities soon procured him a considerable practice, and he was appointed president of the Catholic consistory in 1842. Though socially disadvantaged, the Catholics had remained loyal to the ruling House of Hanover during the 1837 insurrection of the Göttingen Seven against King Ernest Augustus, and in 1848 Windthorst received an appointment at the supreme court of appeal ("Oberappellationsgericht") for the Kingdom of Hanover at Celle. The March Revolution opened for him—as for so many of his contemporaries—the way to public life and though he failed to gain a mandate for the Frankfurt Assembly, he was elected representative for his native district in the second chamber of the reformed Hanoverian parliament in 1849. He belonged to what was called the Greater German party, and opposed the project of reconstituting Germany under the leadership of the Kingdom of Prussia. He defended the government against the liberal and democratic opposition; and, at this time, he began his struggle against the secularization of schools, which continued throughout his life.