Some pain never eases, some horror doesn't relent, but there are times when you are obliged to go back, however unwillingly, to the source.
Not out of any dark voyeurism but the need to understand quite what happened, how it was shaped and how it just might affect something as troubling as the ambivalence, for example, of anyone who ever left the boxing ringside torn between guilt and exhilaration.
On Monday night this opportunity comes to anyone who attended the fight between Nigel Benn and Gerald McClellan at the London Arena in February, 1995, an eviscerating collision which left the latter, an American world middleweight champion of ferocious and clinical talent, consigned to a life of blindness and paralysis.
The ITV documentary, screened at 10.35pm, is both disturbing and brilliant. It throws you back into a lifetime of regret and once again it provokes the question that for some can never be satisfactorily resolved, the one that asks if professional fighting can, in the end, ever be truly justified.
Soon after the shocking scenes in the ring, when in the 10th round McClellan, feeling the first disabling effects of a blood clot, twice went down on one knee, was counted out the second time, then collapsed, a motion for the abolition of boxing was tabled in the House of Commons. It was defeated but no one in the sport had any reason to be sanguine, and least of all those in the hospital who heard the understated words of the surgeon charged with saving McClellan's life. He said: "The brain is swollen but that is what we would expect it to be after being punched for 10 rounds. There is a clot in his brain that will end his career and kill him if it isn't taken out."
McClellan spent 11 days in a coma after the emergency operation and eventually he was taken back to his home in Freeport, Illinois by his sister Lisa, who has cared for him with great devotion ever since. She says now that for many years she wanted Benn dead but admits to being moved by the sight of the British fighter, now a lay preacher, weeping when he embraced her brother at the fundraising event he had organised in the West End of London. "Yes, that was a kind of closure," she admits.
One that is maybe not guaranteed to carry her through all the long nights, but then when you think of the convulsion that came to her brother's life, his violent separation from all the certainties created by a talent that had made him in the eyes of many experts the world's best pound-for-pound, most destructive fighter, still a kind of miracle of emotional endurance.
McClellan was an overwhelming favourite, having successfully defended his World Boxing Council middleweight title three times, all of them inside the first round, when he came to London to challenge Benn for his WBC super-middleweight title and his status was confirmed with withering power as early as the first round. He sent Benn sprawling through the ropes and on to the apron of the ring and one of the agonies that came later, when McClellan, who also floored Benn in the eighth round, began to blink uncontrollably and give, in retrospect the first clear evidence that he was in serious trouble, was the belief of many that the French referee, Alfred Asaro had given the British fighter the benefit of a long count.
"The fight should have been over there and then," Stan Johnson, McClellan's trainer, still insists.
Johnson, though, is one of the documentary's least convincing witnesses, especially when he claims there was no evidence that his fighter had developed a serious problem in the ring and, chillingly, Emma McClellan says that she could not say he was a properly qualified coach of boxers.
Her point is augmented by the famous trainer Emmanuel Steward, who had developed McClellan's talent in his Kronk Gym in Detroit and would have been at ringside in London but for contractual disputes. Steward says that had he been in McClellan's corner the tragedy would not have happened
Johnson accuses Benn of being "juiced up on something", claiming for the first time 15 years after the event that the McClellan corner had "blood" evidence that he was using anabolic steroids. Benn denies the charge vehemently, saying that while he was addicted to "recreational" drugs throughout his career it was "not him" to use the performance enhancing variety, and that when he collapsed on the way back from the ring to his dressing room it was out of exhaustion and not any plan to avoid a post-fight drugs test.
Later, when the plight of his opponent had become clear, he said that he was sorry but, "Better him than me".
It was a sentiment that might, you have to suspect, have slipped as easily from the lips of McClellan had the roles been reversed. Not the least affecting scenes from the film depict the relationship between the stricken fighter and his sister, especially in one when they discuss the roles of the carer and the dependent and she jokes that he might pay her $100. He asks, "What do you want me to do, rob a bank?" They both laugh at the impracticality of the plan.
However, there is no disguising the hard edge of McClellan's nature in pre-fight footage. An interviewer asks him about his status as the world's second best pound-for-pound fighter. McClellan's eyes narrow and he asks: "Who do they say is the first?" It is not so much a question as a bitter reproach.
McClellan trained pit bulls for fighting. He said the breed reminded him of himself. Johnson reports he once asked the fighter why he served up a labrador to his pit bull and says that McClellan responded: "A pit bull is like a fighter. Every so often it needs to taste blood."
The awful trajectory of the fight is perfectly recaptured and the most telling moments are when McClellan, who was comfortably ahead on every scorecard, first began to display distress and confusion, about which Johnson insists there was absolutely no evidence to justify any decision to throw in the towel.
The list of witnesses is long. Among the more eloquent is former world featherweight champion Barry McGuigan, who does not attempt to diminish the horrific consequences of the fight but also makes the point that boxing has saved hundreds of thousands of lives by rescuing young people from the most dangerous streets. It is the classic defence but not so easy to proclaim when the questioning gets a little more specific.
McGuigan suggests that McClellan's corner should have identified a growing problem but then he is asked: "Should the referee have picked up on it?" McGuigan frowns and says: "It's a good question."
But then so many questions littered that night in London's Docklands. You had to wonder if you would ever forget, and would ever be entitled to forget, those terrible scenes in the corner of the ring where McClellan first rested against the post, then slipped down onto the canvas and, finally, was laid out flat. There was the ultimate fear that you were watching a life ebb away and if that was averted by the skill of a young surgeon we would know soon enough that some things could not be retrieved.
It made you think of all the great fights you had seen and how much accumulated damage had come along the way. You thought of the condition of Muhammad Ali, so exacerbated by the gratuitous punishment he took before the end, and not least on a night in Las Vegas when his former sparring partner Larry Holmes was obliged to pound on him for seven rounds before the great old cornerman Angelo Dundee called the surrender.
You remembered the night Sugar Ray Leonard's wife Juanita screamed, "No more baby, no more," when her husband fought Tommy "The Hitman" Hearns to a standstill in one of the greatest contests ever – or when Marvin Hagler and Hearns, again, produced extraordinarily violent action over three rounds.
Benn-McClellan, though a merciless contest, has to be remembered for other reasons. In unremitting detail, it is about to be presented to us again, in all the rawness of the fighters' aspirations and the brutality of the fate of one of them. Also, the inherent danger accompanying any fighter who ever steps into the ring.
Frank Bruno was another witness and he speaks of his absolute absorption in the battle. It is pointed out to him that he sat, when he wasn't jumping up and down, dressed in a red suit, in the company of the promoter Don King, who was quite possibly contemplating the prospects of a rematch. Bruno says that the fight was so compelling he wouldn't have noticed if Mickey Mouse or Batman had occupied a neighbouring seat.
Certainly it was absorbing. What else it was, what else boxing will always be, has rarely been so graphically portrayed. The Fight of Their Lives is illuminating in the darkest possible way.
What James Lawton wrote from ringside
"When they gave Gerald McClellan his fourth injection in the corner of that zoo of a ring, when they put the brace on his neck, and the oxygen mask to his face, and when all the demons of a brutal business crowded in, you were left with the question that will never go away. How long can the old game go on?"