The office fell vacant in 1644, and Parliament appointed Prideaux to the charge of the posts.[29] This task he entered upon with some seriousness, and with considerable success. He extended the service, but raised the minimum postage to 6d. From a report submitted by him to the Council of State in 1649, it appears that he had established "a weekly conveyance of letters into all parts of the nation," and that with the moneys received as postage he had been able to defray the whole cost of the postmasters of England with the exception of those on the Dover Road.[30] At the time of his appointment the posts involved a charge to the State of some £7,000 a year.[31] It might therefore be thought that for Prideaux to be able to carry on the system, to give a despatch of letters to all parts of the kingdom every week, and at the same time make the proceeds of postage cover the whole cost, except for the Dover Road, was a considerable achievement. The Commons were not, however, altogether satisfied. The long disputes between the various patentees, and their anxiety not to lose any part of the business of conveying letters, made it evident that there was a profit other than the salary paid by the King, notwithstanding that funds for the maintenance of the posts were drawn from the Exchequer year by year. The office of Master of the Posts was bought and sold. Witherings sold part of his wife's estate to the value of £105 a year in land to obtain the office. The deputy postmasters also bought their offices. And in 1642, by vote of both Houses, Burlamachi had been required to give an account of the _profits_ of the Letter Office. The Letter Office was in fact not on the simple basis of payment by the messengers to the Master of Posts of all receipts, payment by the Master of Posts from the receipts of the ordinary fixed wages of the deputy postmasters (together with the cost of special expresses) and of his own salary, and payment from the Exchequer of the balance necessary to complete such payment. The deputy postmasters took, and retained for their own use, the postage received on private letters, paying a percentage to the Master of the Posts; and they had also the monopoly, which was very lucrative, of letting horses to travellers riding post. In view of these profits they were prepared to purchase from the Master of the Posts the office of deputy postmaster, and sums received from that source, together with the percentage of the postage of private letters, constituted the emoluments of the Master of the Posts, additional to his salary. The Commons, being no doubt aware of this, concluded that there ought to be a net revenue from the Office, and required Prideaux to pay the sum of £5,000 a year.[32]