London - Four-time Tour de France champion Chris Froome said on Tuesday that being cleared of doping allegations had lifted a "huge weight" from his shoulders, describing the saga as "like your worst nightmare".
The British rider had been barred from taking part in world cycling's biggest race, which gets underway on Saturday, until organisers dramatically lifted the ban on Monday.
Froome, 33, told the Times in a interview he felt dizzy last year when a lawyer from the sport's governing body, the Union Cycliste Internationale (UCI), informed him he had recorded more than the allowed dose of the legal asthma drug Salbutamol during September's Vuelta a Espana.
"It has been like your worst nightmare," said Kenyan-born Froome, speaking to The Times from his apartment in Monte Carlo.
"It was the phone call I never thought I would ever receive.
"Tim Kerrison (his Team Sky Australian coach) was walking around and I told him, 'I can't believe what I just heard'.
"You do everything right then this nightmare. I actually felt dizzy. I climbed off (a turbo trainer) and immediately just started googling to learn what I could about Salbutamol, about thresholds."
Froome won the Vuelta and went on to add the Giro this year, storming to victory with a remarkable 80-kilometre (50-mile) breakaway in the mountainous 19th stage that turned a deficit of more than three minutes into a 40-second lead.
Tour organisers dropped their opposition to Froome racing mere hours after the Swiss-based UCI confirmed it had cleared Froome of doping suspicions.
"These were severe allegations," said Froome.
"For an athlete it doesn't get much worse," he said.
"This was a nightmare scenario for any clean athlete. It was challenging to a level I've never experienced before.
"For any athlete, to go through something like this, it can define your career.
"If you've done something wrong, that stays with you forever. So it's a huge weight off my shoulders."
Froome said he has received endless calls, including from school friends from South Africa, telling him they knew the truth would come out in the end.
He is expected to face a hostile reception from some Tour spectators.
If Froome wins he will become only the third rider in history - along with Eddy Merckx and Bernard Hinault - to be the reigning champion in all three of cycling's Grand Tours.
Frech icon Hinault, known as the "Badger", said prior to Froome's being cleared that the peleton should go on strike if the British rider starts.
However Froome said he would not give the five-time winner the cold shoulder.
"I can't say anything bad about Bernard," he said.
"He's one of the great champions.
"I imagine with age sometimes your wires get a little bit crossed, but if I see him I'll very happily explain it all in a bit more detail... because he certainly got the wrong end of the stick."
So driven is Froome that he said he will not leave the Tour even if his wife Michelle, who is eight months pregnant, goes into labour. The baby is due on August 1, just a few days after the Tour reaches its climax in Paris.
"I'll hopefully be back in time but there are no guarantees," he said.
"I've had team-mates miss births to stay and support me in the Tour so if I was in that position I couldn't let them down.
"Michelle understands that 100 per cent. It's a huge sacrifice but that comes with the territory."