For the past three decades Steve Davis has replayed that shot over and over in his mind and potted it every time. Why would there be any other outcome? It was, after all, a relatively straightforward black, one any ordinary player would comfortably sink.
Davis was no ordinary player. He was the reigning world snooker champion, one of the best-ever exponents of the game and on the cusp of sporting history; an unprecedented third successive title at the Crucible Theatre would be his, as soon as that ball dropped.
But it didn't. Commentator "Whispering" Ted Lowe, overcome by the sensational late twist in the tale, famously yelled out an astonished "No!" as the black rattled the jaws of the pocket and rolled back into play.
To those of us over 40, this demands one of those classic "where were you?" questions.
And for 18.5 million, the answer is: glued to the nearest television, gripped, bleary-eyed and open-mouthed.
Me? I was alone in a London hotel; my advanced shorthand exam was at 9am the following morning. The plan? Early to bed, maybe watch a bit of the snooker to help get me over; not really bothered, that boring robot Davis is going to win anyway ...
It's the stuff of legend that the huge audience that Bank Holiday weekend was bolstered by errant students bunking off from cramming for their own particular finals; like me, who had only a passing interest in snooker, they were sucked in by the unfolding, tension-drenched drama being played out on a 12ft x 6ft piece of green baize in Sheffield.
Dennis Taylor certainly remembers where he was as the clock hit 12.19am on Monday, April 29, 1985; standing over the ball that a disbelieving Davis had just inexplicably missed, and about to complete one of the most staggering comebacks in sporting history.
Over the course of 35 frames, the man from Co Tyrone had never once been ahead. This - the final ball, of the final frame, of a nail-shredding final that had lasted a record 14 hours 50 minutes - would change all that, and become HIS moment of destiny.
Everyone remembers what followed; Taylor's unrestrained, cue-pumping, finger-wagging, trophy-kissing elation as a traumatised, ashen-faced, speechless Davis sloped away.
This newspaper has often documented what a life-changing moment it was for the genial Taylor, who has always admitted he wasn't in the same league as Davis.
But, unlike the then 27-year-old from Essex, the then 36-year-old from Coalisland with the oversized "upside-down" spectacles took his chance to sink the game's most famous black when it really mattered. And in front of what remains the UK's largest post-midnight audience for any programme, on any channel.
"Miracle Man" was The Sun's front page banner headline next day. Yes, you read that right; FRONT page ...
We're coming up to the 30th anniversary of that unforgettable occasion. BBC, which introduced snooker to the masses in the late 70s, has plans to "celebrate" it, prompting Davis to retort recently on BBC Radio Five Live: "Why don't they 'celebrate' the anniversaries of the finals I actually won?"
He's being disingenuous. He knows full well he's remembered more for losing that final than any of his six world championship triumphs.
And it's no coincidence that his new book, Interesting: My Autobiography, has just hit the bookshelves.
It chronicles the life of the man who has won more pro snooker titles than any other; 28 ranking events, 53 non-ranking. "Interesting" is, of course, the ironic, sarcastic label bestowed on him by the Spitting Image puppet series.
Ironic because Steve Davis, OBE, MBE and former BBC Sports Personality of the Year, I'm a Celebrity ... Get Me Out of Here! contestant - and, erm, Rear of the Year - has always been a lot more interesting that the wiry, ginger-haired, anally retentive, Marmite sandwich-loving figure he once painted.
Now based in Brentwood, Essex, the 57-year-old is a pro-standard poker player, a renowned authority on progressive rock bands (with his own radio show), a brilliant cook who has published three books of his own recipes and a formidable chess player who has served as president of the British Chess Federation and co-authored two books on the board game. Oh, and a respected TV commentator, of course.
And although he was once famously quoted as saying snooker was better than sex, he still took enough time away from the table to wed air stewardess Judith Greig (they divorced in 2005 after 15 years of marriage), father two children (Greg and Jack, now in their mid-20s) and squeeze in what the tabloids called a "torrid affair" with a teenage dancer.
It was that final, however, that began to transform his insipid image, although Davis wasn't aware of it at the time. He was too busy dealing with the psychological pain inflicted by a catastrophe he simply hadn't seen coming.
Indeed, a week after the defeat, Davis, en route to an exhibition in Sheffield, threw up in his car as he drove past the Crucible.
"Looking back now, that setback was probably good for my soul," says the man once nicknamed "The Nugget", because at that time he was indisputably the sport's golden boy.
"In the public's eyes I was suddenly a human being with real emotions, not the robot they thought I was."
Davis admits he was complacent about facing the unfancied Taylor that pivotal weekend.
"I'd won three of the previous four world finals and assumed I'd win this one, although I didn't say it out loud," he recalls.
"I'd always done well against Dennis, including one final (the 1981 Jameson International) where I beat him 9-0.
"For me, this one wouldn't be any different. And history shows I went 8-0 up, needing just 10 of the next 27 frames to win ... but then the wheels fell off."
A difficult green in the ninth frame would have made it 9-0; Davis missed, didn't think much of it at the time, but, retrospectively, this was a major turning point.
Taylor, who had been facing utter public humiliation, eventually took that frame ... and six of the next seven. Game on.
"I suffered my worst ever night's sleep after that session," Davis recalls.
"I was still two frames ahead [at 9-7], but I was distraught ... and, psychologically, I never really recovered from letting that massive lead slip.
"Thirty years on, I still wonder what would have happened if I'd just played safe on that green."
He adds: "During the final frame, which lasted nearly 70 minutes, neither of us could really pot anything. We were completely shot after two days of playing 35 frames.
"I was getting whiter and whiter and Dennis redder and redder, to a shade of lobster never seen before, as the pressure mounted. And, in the end, it all came down to one ball."
Davis realises it took a long time to cope with the anguish of that Crucible meltdown, but, as he explains: "We didn't have psychoanalysts then; just mates who said 'never mind, let's have a beer'...
"For me, it was a 'Sliding Doors' moment; I might never have won another title and a shrink would have had a problem getting me over the next three decades."
Davis reached the world final again in 1986 - and lost again, to fellow Englishman Joe Johnston.
But that was different - he was well beaten, 18-12, by a man in the form of his life. No complaints.
But world titles followed in 1987, 88 and 89 (the hitherto elusive three in a row), cementing Davis's legacy as one of the best snooker players of all time.
Taylor, who once scraped a living selling televisions, pocketed £60,000 by winning that Dennis v Goliath encounter; a then record prize for snooker.
He upped his profile, lost weight, restyled his hair and ultimately split from his first wife, Pat, with whom he had two children, Denise and Damian.
But Dennis, now 66, never again reached the heights of '85 and retired from playing in 2000, forging a lucrative career as a snooker commentator and after-dinner and corporate motivational speaker.
Davis often joins him for sports lunches, when "The Black Ball Final" is recalled in forensic detail.
A keen charity worker, amateur golfer and dancer (he finished eighth in Strictly Come Dancing 2005), Dennis, who was already a grandfather, became a father again in his mid-50s when second wife Louise gave birth to a boy, Cameron. They live in Llay, near Wrexham.
For Davis, meanwhile, there was a silver lining of sorts from 1985; seeing Taylor, a man he'd always admired, finally getting the respect he deserved as a player.
"Some never got it because they never won a world title," he says. "It's a shame, but professional sport's like that."
Davis cites a classic example of how ruthless professional sport can be; not long after the Crucible calamity, his closest pal and manager, Barry Hearn, recruited Taylor for his Matchroom stable of snooker stars.
"He marched straight over and said: 'I've just snared the new world champion; what do you think of that?'"
John Laverty is the Belfast Telegraph's executive editor