The idea, however, of giving to Holland a slice of cis-Rhenan territory had perforce to be abandoned in the face of Prussian objections. The preliminary Treaty of Peace signed at Paris on May 30, 1814, was purposely vague, Art. VI merely declaring that “Holland placed under the sovereignty of the House of Orange shall receive an increase of territory—un accroissement de territoire"; but a secret article defined this increase as “the countries comprised between the sea, the frontiers of France, as defined by the present treaty; and the Meuse shall be united in perpetuity to Holland. The frontiers on the right bank of the Meuse shall be regulated in accordance with the military requirements of Holland and her neighbours.” In other words the whole of Belgium as far as the Meuse was to be annexed to Holland; beyond the Meuse the military requirements of Prussia were to be consulted.
Previously to this, Castlereagh had written to the British Minister at the Hague, Lord Clancarty, suggesting that the Sovereign-Prince should summon a meeting of an equal number of Dutch and Belgian notables to draw up a project of union to be presented to the Allied Sovereigns at Paris for their approbation. But William had already himself, with the assistance of his minister Van Nagell, drawn up in eight articles the fundamental conditions for the constitution of the new State; and, after revision by Falck and Lord Clancarty, he in person took them to Paris. They were laid by Clancarty before the plenipotentiaries, and were adopted by the Allied Sovereigns assembled in London on June 21, 1814. The principles which animated them were set forth in a protocol which breathes throughout a spirit of fairness and conciliation—but all was marred by the final clause—Elles mettent ces principes en execution en vertu de leur droit de conquete de la Belgique. To unite Belgium to Holland, as a conquered dependency, could not fail to arouse bad feelings; and thus to proclaim it openly was a very grave mistake. It was not thus that that “perfect amalgamation” of the two countries, at which, according to the protocol, the Great Powers aimed, was likely to be effected.