For every level of society inside and outside Mexico, cantinas serve as both toxin and tonic for drink, song, jocularity, wit, mayhem and mishap. Tio Pepe, now thought to be the oldest such bar in the old Aztec capital, has provided both in equal measure since way before it received its present name in 1878. The cantina is nowadays a refuge for Mexican politicians, as the nation’s state department and the city’s supreme court sit in front of it. On a Tuesday at noon, we found a huddle of operatives gathered in a booth arguing amid cocktails. We sat down with Don Sebastian Alvarez, who took up bartending at Tío Pepe in 1987, a witness to the ebb and flow of politicians, luminaries and troublemakers passing through the doors.