 During the negotiations for the first and second Paris peace treaty and subsequently at the Congress of Vienna he was successful in defending Jewish rights but failed in his attempt to secure a liberal constitution for the German Confederation (Deutscher Bund) to be based on a statute of fundamental principles (Grundgesetz) that would have guaranteed the rights of all citizen. After representing Prussia at the newly constituted Bundestag in Frankfurt on Main for a short time, he was appointed Prussian ambassador to the Saint James Court in London where, besides studying Sanskrit at the British Museum Library in his spare time, he was able, with the help of the Banking House of Rothschild, to organize a financial aid program for the reconstruction of the war-ravished Prussian economy. He returned to Berlin to the ministry of the Interior to head a committee to draft a new Prussian constitution in 1819. But his carefully designed comprehensive plan for introducing a liberal constitution (GS Vol 2: 389–455) that would have transformed Prussia into a genuine constitutional monarchy did not have a chance to be adopted. When Humboldt strongly resisted the repressive measures taken by the royal government in the wake of the Karlsbad decrees and in the ensuing assault on civil liberties, King Friedrich Wilhelm III on New Years Eve of 1819 summarily dismissed him from all his duties. His dismissal marked not only the end of his political career but the de facto elimination in Prussia of the chances for the development of a true civil society, the creation of democratic institutions and thus for the middle classes to participate actively in the political life of the country. Aside from a prolonged visit to Paris and London in 1828, Humboldt spent the rest of his life at the family estate in Tegel which he had renowned architect Karl Friedrich Schinkel remodel in classicist style. There he concentrated his energy on his scholarly and linguistic work.