Immediately upon receipt of the convention in Paris, the French fleet at Cherbourg was ordered to unite with the British squadron at Spithead. This junction was duly effected, and, on November 4, the King of the Netherlands having declined to comply with the demand which had been presented to him, the combined fleets set sail for the mouth of the Scheldt, whilst, two days later, both governments laid an embargo upon the Dutch shipping within their ports. The Duc de Broglie, in the meanwhile, had instructed La Tour-Maubourg, the French minister at Brussels, to negotiate a convention for the entry of a French army into Belgium. The French government had always insisted that the operations, for the reduction of the citadel of Antwerp, must be carried out exclusively by its own troops. The Belgian army was to be entirely separated from them, and was to do no more than hold itself in readiness to repel an invasion, should the Dutch make an incursion across their frontiers. King Leopold reluctantly assented to these conditions, which necessarily deprived his people of an excellent opportunity of wiping out their humiliations of the year before. It came, therefore, as a disagreeable surprise when, on the occasion of the exchange of the ratifications of the convention, La Tour-Maubourg handed in a statement reserving to the French government the right of demanding payment for the expenses of the expedition. This claim, it was afterwards explained, would not be enforced immediately, but would be allowed to stand over until some future occasion. In Palmerston's opinion, however, the fact that payment was to be deferred made the demand no less objectionable. Were it to be admitted, Belgium must necessarily be placed in a position of dangerous dependence upon France. His vigorous protests achieved the desired result. After some discussion the French government agreed to abandon its claim for the repayment of its expenses.[261] In all other respects matters proceeded with perfect smoothness. In accordance with the terms of the convention, on November 16th, a French force of 60,000 men, under the command of Marshal Gérard, crossed the Belgian frontier and laid siege to the citadel of Antwerp, the Duc d'Orléans and the Duc de Nemours, the two eldest sons of Louis Philippe, accompanying the headquarters staff of the army of operations.