The 1967 Tour will always be remembered as the one in which Tom Simpson died on Mont Ventoux.
Tom Simpson: Tragic British Tour victim
The best British rider of his day was a victim of the heat, his own limitless determination and also, sadly, doping.
The riders of the 1960s were not quite the "convicts of the road" of the 1920s but demands still weighed heavily, not least from commercial employers.
These were still a factor even if the 1967 Tour had briefly seen national teams back in the race.
It is widely accepted the drugs were a way of life, to ease the pain if not to improve performance.
And while every Tour rider must know how to suffer, Simpson's problem was that he did not know how to stop.
The rider had taken amphetamines when he collapsed, and his death led to the first drug tests on the Tour in 1968.
1967: Roger Pingeon (Fra)
1968: Jan Janssen (Ned)
1969: Eddy Merckx (Bel)
1970: Eddy Merckx (Bel)
1971: Eddy Merckx (Bel)
1972: Eddy Merckx (Bel)
1973: Luis Ocana (Spa)
1974: Eddy Merckx (Bel)
1975: Bernard Thevenet (Fra)
1976: Lucien Van Impe (Bel)
1977: Bernard Thevenet (Fra)
Cycling's first great drugs shock improved things for a time.
In retrospect, 1967 and 1968 were "eternal second" Raymond Poulidor's big chance.
But "Pou Pou" suffered nothing but bad luck in the two years between Jacques Anquetil's last Tour and Eddy Merckx's first.
Crashes allowed unsung riders to keep warm the yellow jersey before the greatest rider the sport has ever seen arrived.
Merckx burst onto the scene in 1969, with a stunning debut which earned him his nickname.
He was "the cannibal", ready to devour anything and everyone else on the road.
Winning margins had fallen since the 20 and 30 minutes of the 1950s as the field became more even.
But Merckx had 17 minutes to spare in Paris, after a ride which included a 130km solo effort across the Pyrenees.
Not only did he win the race, but he also took the green jersey for the points classification and the best climbers' prizes.
He remains the only man in history to have won a clean sweep and any cycling writer would stake their lives on it never happening again.
Merckx driving on for yet another win
The following year Merckx did allow compatriot Walter Goderfoot to win the green jersey.
But domination was almost total; overall victory, an incredible eight stages and the mountains prize.
Merckx did not just win the Tour in style. There is not a major race he did not win, usually on more than one occasion.
The event could be a single day classic in the cold of spring or autumn or a three-week summer marathon. He won 250 major races, one a week for six years.
Of modern sports stars, only Michael Schumacher and Tiger Woods come close to this sort of dominance and commentators agree the world will never see another cyclist of his kind.
Such domination, by a Belgian, did not make Merckx a popular man with the French.
Most were delighted when he received an unexpected challenge in 1971.
Spanish climber Luis Ocana gained eight minutes' advantage over the Belgian.
But Merckx was lucky as well as brilliant.
When both men crashed in the Pyrenees, the Cannibal rode away while Ocana was hospitalised.
DURING THIS ERA
The first prologue time trial was held in 1976
First drug controls in 1968, a year after Simpson's death
1975: The modern king of the mountains is born as the polka dot jersey is introduced
The same year was also the first time the white jersey was awarded to the best young rider
He had no need to rely on good fortune in winning the 1972 Tour, even if the rest were getting closer to him.
There was to be no attempt at the five consecutive victories that Miguel Indurain was to achieve two decades later, and Merckx sat out the 1973 Tour.
That offered Poulidor hope of finally winning a Tour. The "eternal second" was still a regular top-10 finisher as Merckx dominated.
But Poulidor crashed in the same spot as Ocana had in 1971, allowing the Spaniard to win the Tour this time.
The unlucky Poulidor was back in second place in 1974, pushing the returning Merckx all the way at the age of 38.
All of France hoped their hero would end the Belgian's reign but it was not to be and a younger Frenchman eventually did so the following year.
Bernard Thevenet defeated Merckx in 1975, after the Belgian was punched and knocked from his bike by a jealous French fan.
To be fair he recovered from the incident to ride strongly, and was beaten fairly by Thevenet, who started off a new golden era in France.
Merckx finished sixth in his last Tour in 1977 while poor old Poulidor finally gave up trying after finishing an amazing third, aged 40, in 1976.
France celebrated Thevenet's second win in 1977 and there were seven more home wins until the last, in 1985.
But the Merckx years are a distant memory for Belgium, who have not won the race since Lucien Van Impe's sole 1976 victory.
The race's next hero was a blunt Frenchman from Brittany, who would become the third man to win five Tours.