The result was the Concert of Europe, also known as the "Congress System". It was the balance of power that existed in Europe from 1815 until the early 20th century. Its founding members were the United Kingdom, Austrian Empire, Russian Empire and Kingdom of Prussia, the members of the Quadruple Alliance responsible for the downfall of the First French Empire; in time France became established as a fifth member of the concert. At first, the leading personalities of the system were British foreign secretary Lord Castlereagh, Austrian chancellor Klemens Wenzel, Prince von Metternich and Tsar Alexander I of Russia.