The walls of John’s Grill a few blocks south of Union Square are a veritable who’s who of San Francisco’s power players.

From mayors and police chiefs to journalists and detectives, the mugs of many of The City’s movers and shakers have been decorating the restaurant for more than three decades, said Lee Houskeeper, who represents the family-owned restaurant’s owners.

Today, Mayor Ed Lee’s headshot will become part of the scenery. The ceremony will include former Mayor Willie Brown, Police Chief Greg Suhr, Fire Chief Joanne Hayes-White and state Sen. Mark Leno.

After the 1 p.m. “hanging,” as Houskeeper called it, the guests will eat lunch.

The tradition began in 1968 when then-owner Gus Konstin put up the pictures of retired Mayor George Christopher and retired Police Chief Thomas Cahill. Both men were daily customers and their photos went up above their separate tables, said Houskeeper.

Current John’s Grill owner John Konstin, 50, recalls the day when the late Mayor George Moscone’s photo went up in the ’70s. The spot where it went up was toward the back and the room was filled with Moscone’s staff as well as some politicos, Konstin said. His father opened a bottle of Champagne and the mayor ate his usual dish, Petrale sole.

The memory of Moscone’s photo hanging still sticks with Konstin because Moscone was assassinated so soon afterward.