Some six miles from this bleak mountain top Marco Pantani looked down at his front wheel and shook his head. It was impossible to tell whether it was a gesture of resignation at the knowledge that he could not match Lance Armstrong's pace or disbelief at the speed with which the Texan was pulling away up the one-in-10 slopes. Either would have been appropriate.

Last year Armstrong effectively won the Tour when he blew away Alex Zulle and Fernando Escartin at the first mountain-top finish, Sestriere in Italy, and yesterday he took the yellow jersey with a demonstration of absolute physical supremacy that may prove equally conclusive.

As on the stage to Sestriere, yesterday's 128 miles were a sodden, chilly purgatory, more worthy of late autumn than high summer. Waterfalls overflowed, torrents washed gravel off the mountain sides, the cyclists squelched in and out of banks of dank mist and each man ended the day chilled to the marrow.

The way in which Armstrong turned events in his favour when they were against him was worthy of cycling's greats. At the foot of the eight-mile ascent to the finish he looked vulnerable and isolated. His team-mates in the US Postal Service squad had fallen away on the previous massive climb, the 10 miles to the twin cols of the Aubisque and Soulor, whereas Pantani and the 1997 winner Jan Ullrich both had domestiques to support them.

The climbers Richard Virenque - who has come second and third overall in the past - and Escartin, last year's third finisher, had ridden into the mist on the Aubisque and were leading by two minutes. "It was a bit of a crisis," Armstrong admitted. "I had no team-mates and I had no idea what to do. Everyone was waiting for an attack from Pantani." Pantani bounded out of the group in the style which won him the 1998 race but the crisis was a figment of Armstrong's imagination.

Zulle followed Pantani but the Swiss fell away. Then, remarkably, as Armstrong made the pace, Pantani faltered. Later, he said he had made a mistake in trying to follow the Texan. What followed was almost supernatural, with Armstrong seeming to spin the pedals at twice the speed of the rest. Within a few miles he was bearing down on Virenque's and Escartin's little band and, after a few seconds with them, was speeding away on his own.

The Spaniard Javier Otxoa had started the climb 12 minutes ahead of Armstrong, looking a certain winner. He hung on painfully, after almost 100 miles in front - and took over the best-climber's jersey after winning all five climbs - but Armstrong was not far behind.

Afterwards the comments of fellow cyclists resembled those made after the ride that defined Miguel Indurain's career - the time-trial at Luxembourg in 1992. "Armstrong was like an aeroplane," said Virenque. "He is in a class of his own," said Pantani.

To take such a beating on their own terrain will leave the mountaineers puzzled. While Virenque's and Escartin's losses were at least respectable - one minute 15 seconds and 1:20 respectively - yesterday was a disaster for Pantani, who finished more than five minutes behind, ending his chances of repeating his 1998 victory.

The man who began the day in yellow, Alberto Elli of Italy, was in trouble on the Marie-Blanque and lost more than half an hour, leaving the overall standings transformed. Ullrich's loss of three minutes 19 seconds leaves him second, more than four minutes back, which could be recouped if Armstrong has a bad day.