The report which Prideaux made to the Council of State had another result, which probably he little contemplated. In that report he had taken credit to himself that, although the charges of management had risen to £7000 a year, or about twice the amount they had been in Witherings's time, he had relieved the State from the whole of this burden. In other words, the posts had become self-supporting, but, so far as appeared from the report, were nothing more. The House of Commons was not satisfied. Accordingly the Council was instructed to examine and report whether the terms on which the letter office was held were the best that could be obtained. The investigation was soon made. Heretofore, in consideration of his defraying the charges, Prideaux had been allowed to receive the postage and make what he could out of it. For the future, besides defraying the charges, he was to pay to the State a fixed rent of £5000 a year. This was the introduction of the system of farming, a system which, as regards the posts generally, continued to nearly the end of the seventeenth and, as regards the by-posts, beyond the middle of the eighteenth century. In 1653 Prideaux ceased to be Master of the Posts. Two years before he had been elected a member of the Council of State, and shortly after his election, and probably as a consequence of it, the arrangements for communicating with the army had reached a high state of perfection. Between the Council and the forces in Scotland messengers, we are told, were passing almost every hour. But, useful as he may have made himself, Prideaux seems to have been altogether wanting in those qualities which are calculated to inspire confidence. At the Treaty of Uxbridge, where he was one of the commissioners, even his own colleagues had regarded him as a spy. This feeling of distrust may possibly explain how it happened that, after the expulsion of the Long Parliament, he was forced to content himself with his appointment as Attorney-General. The Council of State, as then reconstructed, did not include him among its members, and one of the first acts of the new Council was to relieve him from the responsibilities of the letter office. Grasping as he was, it is impossible to suppose that this can have been done by his own wish, for the appointment of Master of the Posts, though weighted with a rent of £5000 a year, was still a very lucrative one. His successor paid a rent of double that amount, and is reputed to have derived from his farm an enormous profit.