It is general knowledge that prepayment could be shown in manuscript before 1853, but only by stamps (or postal stationery equivalent) after 1853. Can anyone give me a reference to how this information was communicated/ enforced, or to the actual date?
Thanks
Peter Chadwick

It is well recognised that red indicated "prepaid", black unprepaid, at least by 5 Dec 1839. Can anyone tell me when this convention first started to be used?
From Peter Chadwick