The clamour of momentous achievement had yet to descend from Kinshasa and the only other people present were Ali's bodyguard, a Chicago policeman Pat Patterson, his aunt Coretta Clay and the other cook Lanna Shabazz, who was fixing a meal for him.
Foreman had landed some heavy punches, but apart from a small bruise beneath the right eye, Ali was unmarked. Dressed in black slacks and matching black shirt, he was sitting back in an easy chair with his legs stretched across a low table. That alarming decision to fight Foreman off the ropes brought to a glorious conclusion, he said. "There he was swingin' away and all the time I was talkin' to him sayin': 'Hit harder, George. That the best you got? Harder, sucker, swing harder. You the champion and you gettin' nowhere'. Then pop! I'd stick him with a jab."
Partly because it was unusual to hear Ali swear (he first checked to ensure that the ladies were out of earshot), the thing I most remember Ali saying was: "I done fucked up a lot of minds."
Sadly, the probable long-term effects of that and subsequent contests (as well as risks taken in sparring to be confident of withstanding the heaviest punishment) has long since occupied our attention.
This week, I went along to an exhibition of photographs by Ali's long- time friend Howard Bingham, coinciding with tomorrow's London release of When We Were Kings, a vivid, Oscar-winning account of the most dramatic event sport has ever known.
For those of us who rode the jet stream of Ali's stupendous progress, sights of him in full flow, talking up a storm, soaring from one flight of fantasy to the next, are bound to bring on sadness.
Motor senses numbed by the onset of Parkinson's Syndrome make him tread carefully now, the measured steps symptomatic of a condition surely caused by too many head punches. People say that within its confines Ali remains happy, intellectually sound.
"When something catches Ali's interest, the response is immediate," Bingham said. "For a moment suddenly he rolls back the years. I think he enjoys life, I really do."
That view is shared by Benn Wett, who has spent three months on a documentary about Ali as he is now that will be shown next week on German television. Close to Ali for 30 years, he came across encouraging examples of his awareness.
"Howard is absolutely right," he said. "If something interests Ali he becomes, however briefly, almost his old self again.
"A short while ago in Chicago, he grabbed my arm and edged towards a framed picture of him boxing. He'd identified the other guy. 'Jurgen Blin,' he said. Now that wasn't one of Ali's big fights and it took place in Zurich in 1971, so his memory appears to be intact."
More recently, Wett was asked if Ali could handle a short tribute at a ceremony to mark the 50th anniversary of Jackie Robinson's breakthrough as the first black player in Major League baseball. "I didn't want to embarrass Ali, but when I mentioned Robinson's name that old smile came to his face. 'Is he dead?' he asked. It would have been enough for him to say 'Jackie, you were great' but, astonishingly, he went further, adding: 'The greatest, the greatest of all times, greater than I ever was'."
Ali's performance at an event put on for children in Pensacola, Florida, by the light-heavyweight champion, Roy Jones, surprised Wett even more. "Roy persuaded Ali to get involved and, astonishingly, he got up on his toes and started shadow boxing. Larry Merchant of HBO was there and shared my amazement. 'Did you see that?' he said. 'For a few moments the light was back in his eyes'. I don't think Ali is sad and he gets a lot of loving care from his wife, Lannie. The great thing, of course, is that as sport's supreme hero he still commands a great deal of attention'."
There has recently been a suggestion that Ali may benefit from a new treatment. I don't know about this but there is no sense in doubting the probability that his plight is linked directly to boxing.
When We Were Kings is a smashing film, but it only proves that Zaire was indeed the time to start worrying about him.