The American levelled the infamous slopes of the Alpe d’Huez, finishing over a minute ahead of his nearest rival to win his second stage of the 91st Tour.
The young Italian Ivan Basso was the only rider who could have harboured serious ambitions of overtaking Armstrong before Paris as he trailed him by one minute, 25 seconds this morning.
But Armstrong emphasised his superiority by surging past Basso, who had started two minutes ahead of him, before finishing a further 22 seconds ahead of the CSC rider.
With just one more mountain stage to come - tomorrow’s route over the formidable Col de la Madeleine - Armstrong, if he stays on his bike, will go beyond the sport’s immortals - Eddy Merckx, Jacques Anquetil, Bernard Hinault and Miguel Indurain - in winning a sixth consecutive Tour.
The French call the time-trial the race of truth - cycling stripped of everything but cold numbers.
This year the Tour committee gave the phrase new emphasis by choosing the ‘Alpe’ - where reputations have been made and spirits broken over the years - to stage the time-trial.
The numbers here are terrifying: average gradient 7.9%, the road rising 1,130m in 15.5kms through 21 hairpins numbered in reverse order.
Armstrong had to add weight to his carbon-fibre bike as it fell below the UCI’s minimum of 6.8kg by 20 grams.
But that was the only occasion that the numbers worked against him all day.
At the first time check, 1.5km in, the Texan had been three seconds down on Jan Ulrich - who has finished second to Armstrong on three occasions.
The German was making good time but by the second check, after 9.5km, he had been superseded with Armstrong surging ahead by 40 seconds
At the finishing line, Ulrich was only the best of the rest, over a minute behind Armstrong.
The authorities estimated around a million people had crowded on to the mountain, some of them arriving a fortnight ago.
As always, with the narrow roads thick with flags and people, a few times the race teetered on the edge of disaster.
Armstrong criticised the decision to hold the time-trial on the ‘Alpe’.
He said: “Quite frankly, I think that it’s a really bad idea to do a time-trial on this mountain. There’s too much at stake.
“You’ve got people on the side of this mountain for over a week and they’ve been drinking all day and they’re getting angry.”
The stage was dedicated to the memory of Marco Pantani, the Italian cyclist who died earlier this year after losing a battle against cocaine addiction.
Setting the fastest climb up the Alpe was one of Pantani’s achievements but the mountain has also become synonymous with Armstrong.
It was here, three years ago, that he gave Jan Ulrich the famous ‘look’ before dancing up the mountain while the German crumbled behind him.
It was Joseba Beloki’s turn 12 months later as the Basque was broken while Armstrong claimed the stage win thanks in large part to a phenomenal performance from then team-mate Roberto Heras.