Mazarin, the ablest and most successful of ministers, had one damning vice. He was shamefully avaricious. He amassed, in the service of the State, therefore dishonestly, an income larger than that of the King of England or the King of Spain. The necklace of pearls which he gave to one of his nieces, and which is at Rome, is said to be still the finest in existence. But Mazarin, though he was sordid and mean, was a statesman of the highest rank. He sent his niece away, in spite of the tears of Lewis, and the Spanish princess became Queen of France. The independence of Spain, the unity of the Spanish empire, were too grand a thing to be an item in the dowry of a bride. She was compelled to renounce her rights, which were transferred to her sister. The renunciation was conditional. It was to depend on the payment, in due time, of the Infanta's fortune. As the payment was not made, the French regarded the surrender as null and void, and the interest at stake, the most splendid inheritance on earth, was one that could not be given up without a conflict. From the moment of the marriage the main object of French policy was to make the succession secure, by negotiation or force, and to take every advantage otherwise of Spanish weakness. All these plans were doomed to a terrible disappointment. In 1665 Philip of Spain died; but he had married again, and left a son, who became king, in his cradle, under the name of Charles II. The new king was sickly and backward, and it was expected that he would die young, unmarried, and childless. Meantime, the fulfilment of French hopes was postponed for a generation, and the Spanish succession was opened, not at the beginning of Lewis's reign, but at the end. He recovered from the blow by a device to acquire part of the Spanish empire, no longer having a hope of the whole. The device was suggested by Turenne. His experience in the Fronde taught him the danger of having the Spaniards so near, in the valley of the Somme. "Whenever there is trouble in France," he said, "the enemy can be at Paris in four days." In self-defence, for security rather than aggrandisement, the frontier must be pushed back. He caused his secretary to compose a treatise, showing that, by the custom of Brabant, that province devolved on the queen, Maria Theresa. It was the custom there that the children of a first marriage should suffer no loss if their father married again. What would have been their estate, remained their estate. The fee simple passed to them. The father enjoyed a life-interest only, without the power of disposal. The French government argued that, by the analogy of the Salic Law, the principle which applied to property applied to sovereignty, and that what was good for a manor was good for a crown. And they assumed that the custom of Brabant was the law of Belgium.