Great Britain Philatelic Society

Can anyone please tell me when the OHMS endorsements on official mail began? I have some recollection of reading that it was with uniform penny postage in 1840? I attach scans of two covers, one from 1840 with manuscript OHMS to a Scottish procurator fiscal and one 1841, also Scottish, with printed On Her Majesty’s Service to a tax office.

I can't tell you when the OHMS endorsements on official mail began, but here's one from February 1800, so way before your recollection that it might have been 1840.

Many thanks for that Winston, as you say it clearly goes back further than I expected! Has anyone an earlier example?