The legendary driving force behind the early days of the Traverse Theatre in the 1960s, founder of the UK's first paperback bookshop in Edinburgh, counter-cultural polymath and host of the hottest dinner parties in town at his Paris home, has brought two shows to this year's Fringe.
Unlike every other eager- beaver publicity person in town, Haynes doesn't want to oversell them, no matter how remarkable he might think both The Surrender and Broadway Enchante really are.
"I'm wary of recommending things to people," Haynes twinkles, "because they go expecting a 10, and if they only get an eight, then they're disappointed. If they go expecting a five and they get an eight, then they're happy. I call it Jim's law of rising and falling expectations, which is also the critic's dilemma."
Haynes's two shows are very different beasts indeed. Broadway Enchante, as the name suggests, is a homage to the golden age of American musical theatre by French chanteuse Isabelle Georges and a full band.
"It's an investigation into what Broadway musicals are about," says Haynes. "Isabelle is one of these women who fell in love with Judy Garland and musical films from an early age and started tap-dancing.
"I'd met Isabelle in Edinburgh in a show at C venues called Judy and Me, and then I saw her do this show in Paris loved it, and knew they had to take it to Edinburgh."
A solo female performer is at the heart of The Surrender as well, albeit in very different circumstances. "It's a sexual autobiography, I guess," says Haynes of the play, adapted from his friend Toni Bentley's book, published in 2004. The stage version, performed by actress Isabelle Stoffel, has already had a sell-out run at the National Theatre of Spain.
"It's about a woman being dominated," Haynes says, "and is quite outrageous. It's not very PC."
Haynes is also celebrating the 50th anniversary of the Traverse Theatre, which has come a long way since its bohemian beginnings in a former High Street brothel in 1963. Ideally, Haynes would have liked to have brought another old friend back to Edinburgh.
"In 1960 I saw an actress called Jane Quigley in a production of Orpheus Descending when she was a student in Edinburgh and was still called Jane Quigley, and we became lovers. She was the reason I created the Traverse."
As Jane Alexander, she went on to become a star on Broadway and in film, earning herself four Oscar nominations before moving into politics, with the then President Bill Clinton appointing her chairwoman of the National Endowment of the Arts.
"What I really wanted to do," says Haynes, "was to get Jane over to do a show at the Traverse, but they were already fully booked." While ill-health, including a heart-attack scare two years ago, have certainly reminded him of his mortality, Haynes remains tireless in his pursuit of the new. As someone now approaching his 80th birthday, why, one wonders, does he keep on coming back to Edinburgh?
"I'm always gonna' give you a smartass answer to that," he says, "and say that I never go back anywhere, I only go forward. I'm going forward to Edinburgh for the 56th time this year, and I'm very happy about that."
The Surrender, Gilded Balloon; Broadway Enchante, Assembly Hall, both running until August 26.