The footage of Tom Simpson's death, as seen in Death on the Mountain has precisely the kind of unsteadying graininess, enhanced in black and white, that alerts to the gravity of what is being captured. Aesthetically - and for seminality - it is from the Abraham Zapruder school of film, he of the Kennedy assassination.
Simpson is limp and slouched on his cycle, three men steering him to the side of the road. The pedals are pedalling his feet, not the other way round. Soon he is vanished among an onrushing flock of helping men who peel him off the cycle - his hands were locked around the handles - lie him down and try to revive him, unsuccessfully; it is thought he was gone before he hit the ground.
This was from the 1967 Tour de France, Simpson the lead British cyclist of his generation, a sporting hero, on the way up Mont Ventoux, an ascent another rider called "hell on wheels". The cause of death was heart failure, from the heat and exhaustion, but more relevantly, the amphetamines and alcohol found in his body during the post-mortem examination. (Police discovered amphetamine pills in his pocket, too.)
Doping in cycling, or sport, was not new even then. In his book Dying to Win, Barrie Houlihan writes of Greek athletes in the third century taking "varieties of mushrooms to improve their performance". In the 19th century came "reports of competitive swimmers in Amsterdam taking an opium-based drug".
And some cycling coaches, Houlihan points out, were mixing heroin and cocaine for riders around the same time. In fact, the real catalyst for drugs in sport, writes Houlihan, came with the Second World War, when militaries began "extensive and frequently unregulated experimentation with drugs".
Simpson's end though, unmatched resonance provided by TV, became the moment that effectively shaped the response to doping in sport, and it has not changed since.
Imagine watching TV that day in 1967, its captive force multiplying every day like some predatory virus, and seeing a human die in sporting pursuit. And then to discover he died from drug usage. The natural response, with sport still empowering itself away from amateurism, society just forming the idea of recreational drugs as menace, was the hard-line one that doping must be eradicated: it was dangerous, it was a legal breach of sporting code and, so, a moral breach as well.
This stance has remained, hardening with each successive doping scandal. Dr Sigmund Loland, a professor of sport philosophy in Norway, has articulated broadly in journals the rationale for anti-doping.
"Drugs in sport elevate the performance level," he says. "If you want to compete you have to be on drugs. Drugs have a coercive effect limiting the freedom of athletes. Moreover, the responsibility of performance is gradually transferred from athletes to external medical-expert systems.
"Sports is reduced as a sphere of human perfectionism in which individuals cultivate their talent through hard and systematic training. Drugs threaten the spirit of sport as a valued human practice enjoyed by athletes and spectators."
Now imagine going back to that day again, except this time imagine not being so sanctioning, as Dr Bengt Kayser, a sports scientist at the University of Geneva, does.
"Imagine if we said then 'Oh dear, this is not good. Guys, we're going to monitor this better, we want to know what you take and we'll build an evidence base of what works, what doesn't and we'll inform you as best we can. We'll put sanitary measures to prevent unreasonable things so that it doesn't outgrow …'"
Kayser happily admits to being persona non grata to the anti-doping movement. He says he is a realist, whose beliefs stem from the assumption that sport can never be totally free of doping.
This in itself is neither radical nor defeatist. Doping's evolution is such that each scandal has unveiled greater sophistication and wider complicity than the last. Anti-doping plays catch-up; sport is not clean and it might be getting less clean all the time.
Loland accepts this: "Very few if any rules in society function like this: total obedience. People drive too fast and cheat on taxes. This does not mean that traffic rules and taxation laws are useless. There will always be athletes who attempt to cheat."
The head of the World Anti-Doping Agency (Wada), John Fahey also does, recently acknowledging: "this is a fight that, sadly, will never be won." But Kayser's is a deeply considered stance, built not just from legal standpoints, but ethical and philosophical ones, and takes this further, maybe uncomfortably so.
"The objective of anti-doping is zero tolerance, like the war on drugs or prohibition in the US," he says. "In modern society, specifically those that have evolved where the individual's interest is important and have a democratic system, it's impossible to impose. It's illusory to think it will ever be solved. It is very natural for a human engaged in elite sport to look for whatever ways to improve performance.
"There is no intrinsic difference between training methods, vitamins, supplements, ways of eating, sleeping or any technology that allows an edge to athletes. The pressure for using any means is high and it is artificial to make distinctions between what is today considered doping and all other means. It's very human: doping exists and it is artificial to make this distinction and eradicate it."
A provocative editorial in the influential science journal Nature once took this line further, addressing it in particular to the Tour de France, in 2007.
"To be sure, a change in the rules [to allow doping] would lead to the claim that 'the cheats have won'. But as no one can convincingly claim that cheats are not winning now, or have not been winning in the past, that claim is not quite the showstopper it might seem to be."
But then what? If we become fine with doping, if we explicitly allow it, then where do we go? Identifying acceptable and unacceptable drugs, or levels of usage, is too nuanced a distinction for mass appraisal.
To proponents of anti-doping this would be a subversion of the fair-opportunity principle that we strive for in life and sport; that, very broadly, we should all compete on a level footing.
Yet even without doping, athletes don't start equally for all kinds of cultural, sociological, economical and political reasons. If we are not starting with everyone benefiting from fair opportunity, why enforce it at a later stage?
"Of course, this is true," says Loland who has also written a book on the subject, Fair Play. "However, sport is not about equality but about a particular kind of inequality, inequality in performing particular skills built on the cultivation of talent through hard and admirable effort, the spirit of sport, as it is called in the Wada code. Drugs reduce this idea of sport."
Of the many ways to look at the Lance Armstrong case, here are two. It is an "I-told-you-so" for the anti-doping movement, a big name caught and taken down.
"The tale of Armstrong is perhaps that truth will prevail," Loland says. "Current and future cyclists will interpret the story as a strong deterrent. If you perform well on drugs, you cannot feel safe the rest of your career, perhaps life."
Another is to shrug, understand that the Tour was birthed as a nakedly commercial enterprise to raise funds for a magazine, and acknowledge that what Armstrong did, in one way, represents the ethos of the Tour, what the Tour has bred, wanted, and thrived off.
"When Armstrong was doing this, most of the time, the majority of people were excited," Kayser says. "You could argue Armstrong played the game according to the written and unwritten rules and actually responded to what the Tour aspires to, which is that there is a big public and they get excited by it, they like some athletes, not others." (And he made them a lot of money.)
There is appeal to Kayser's arguments, even if the end has no clear shape. There are rational questions: how much do we know about the banned substances on the Wada list and the effects they have on athletes? Why are some drugs even on the list? Why does Wada draw such moral fibre from the war on drugs in society, which, really, is a different battle altogether?
"Pragmatic approaches that go towards living with the problem, trying to constrain it, to control it show promise," Kayser says. "I mean what is sports? It is amusement … OK, it is an industry, but would it be fundamentally different as industry if it tried to accept history and continue living the same way?"
It isn't easy - maybe even right - to imagine this future, a belated exploration of the other response to Simpson's death. But sport is a funny beast, its moral axis in perpetual evolution even as, in the present, it remains sententious. Remember, after all, 50 years ago there was no greater sporting sin than being a professional.