Bismarck described Napoleon III's attempt to change this agreement as "like 'an innkeeper's bill' or a waiter asking for 'a tip'", adding that to do so would be against "plain common sense". During the Franco-Prussian War both sides (as well as Austria and Russia) reaffirmed this agreement through the efforts of the British Foreign Office. Charles de Broqueville was a strong domestic supporter of it, and one country re-affirmed it after being released from the Locarno Pact. Baron de Bassompierre responded to a violation of it with the statement "If we are to be (*) crushed, let us be crushed gloriously" and it was officially broken via a notice delivered to M. Davignon from Fritz von Below. Chancellor Bethmann Hollweg called its official document a "scrap of paper", and it was first enacted in 1839. Kaiser Wilhelm attempted to barter this away from King Leopold for two million pounds sterling. For 10 points, identify this policy guaranteed by the "Concert of Europe" via the Treaty of London, violated twice in 1914 and 1940 by German invasions of a certain Low Country.