An agate cameo ring, 19th century, set with an oval agate cameo depicting a tragic Greek theatre mask over the double-faced god Janus, to a gold mount with engraved floral shoulders, size 6 1/2

London In Roman mythology, Janus was a king of Latium (a region of central Italy), who had his palace on the Janiculum hill, on the western bank of the River Tiber. According to the Roman intellectual Macrobius, Janus was given divine honours on account of his own religious devotion, as he set a pious example for all his people. Janus was proudly venerated as a uniquely Roman god, rather than one adopted from the Greek pantheon. All forms of transition came within his purview – beginnings and endings, entrances, exits, and passageways. The name Janus (Ianus in Latin, as the alphabet had no j) is etymologically related to ianua, the Latin word for door. Janus himself was the ianitor, or doorkeeper, of the heavens. The cult statue of Janus depicted the god bearded with two heads. This meant that he could see forwards and backwards and inside and outside simultaneously without turning around. Janus held a staff in his right hand, in order to guide travellers along the correct route, and a key in his left to open gates.