The seizure of the mails was doubtless due to a desire on the part of the Council to discover such persons as might be holding correspondence with the enemy. The vigilance of the Council continued, for, on 4th December, the Deputy Governor of Dover was required to examine the master of the post barque, lately come over, as to his bringing a person who (as he had been previously informed) "was dangerous, and brought commissions and letters from the enemy." And, again, on the 13th May 1651, the Council of State gave order to the Committee of Examinations, "to inquire into the opening of Capt. Bishop's letter between England and Scotland, and to write such persons as they think fit for the discovery of the same. The Attorney-General to bring in a list of the persons employed as postmasters upon the several roads throughout this nation, with their character." "To write the Lord General to cause an inquiry to be made after the persons who presumed to break open some letters directed to him, and, if he finds any of them to be near the southern parts, he is to give notice thereof to Council, that they may prosecute them."
Again, on the 21st August 1651, the Council gave directions that "the packet brought in this day from the northern parts be searched before the letters be delivered out." These are specimens of the measures taken at the period in question with the view of preventing the post-office service being used in the interest of the King's party.