By the enactment of 1710 (England) a special warrant was required for each opening or detention of correspondence. For a long time great laxity prevailed in following this procedure, and the constant tampering with the public correspondence elicited strong protests from Parliament in 1723, and again in 1735, when it appeared that a regular system of examination existed. A committee of enquiry found this to be an infringement of privilege.

In 1806 a system of recording dates of warrants issued was initiated; but in 1844 public attention was again called to the subject by the revelation the correspondence of Mazzini, the Italian political exile, had been systematically examined by the post office officials.

In 1882, during a debate on the question, the House of Commons accepted the statement that powers of examination still rested with the Secretary of State, but were exercised only for state purposes of grave import; and it may be taken for granted that such powers are rarely exercised.