A few minutes later he was riding down a street in a quiet suburb of Nice to the discreet gate of a house, perched on a hillside overlooking the Cote d'Azur, to pick up his training partner. After a few minutes, Hamilton reappeared, another rider, clad in the same team kit, at his side.
That training partner was Lance Armstrong and in the wake of his second Tour win, the Texan was becoming increasingly reclusive. That was perhaps understandable, given that, according to Hamilton's new book, The Secret Race, he and Armstrong were regularly taking a variety of high-octane doping products.
Co-authored with Daniel Coyle, The Secret Race is a visceral, painful and brutal insight into what many claim is the real Legend of Lance and the era he dominated. As a successor to David Millar's Racing Through The Dark, it has opened the floodgates on a new torrent of confessions and long-awaited outings of doping histories.
Not from Armstrong, however, who continues to deny any wrongdoing. Hamilton, he says, is "greedy and self-serving". In his eyes, mired in doping allegations from self-confessed dopers, Armstrong remains the rightful champion, still able to claim the moral high ground. Yet if the whistle-blowers, witnesses and accusers are right, his story is one of megalomania, Machiavellian ruthlessness and breathtaking corruption.
For those – like this writer – who long harboured anxieties over Armstrong and his entourage but, due to the absence of concrete evidence or positive doping tests, were unable to prove them, those suspicions seem finally vindicated. At the heart of it all lies the cynicism of a sport that accepted doping as inevitable.
By the end of his seven-year reign, Armstrong was a monstrous, bullying figure, quick to blacklist his critics, unafraid of any authority and always ready to sue, sue, sue the allegation, rather than answer the question.
Even so, there's no sense of triumph in watching his comeuppance: just a horror of sorts, at how a sport, its audience and its supposed values were so casually and, without even a backward glance, betrayed.
Thirteen years — his first Tour win was in 1999 — is a long time to live what Hamilton and others claim was a lie, but Armstrong never flinched. He still doesn't: he's still coming out swinging, even as he increasingly resembles a punch-drunk heavyweight, holding himself up on the ropes.
But then the Texan has always been a fighter, clean or dirty, and an athlete that Hamilton labelled the "greatest he'd ever seen".
Raised by a single teenage mum, deserted by two fathers, one his birth father, the other his adopted father, he's scrapped and fought throughout his career.
As Coyle noted in his memorable first book on Armstrong, Lance Armstrong's War, the Texan has long resented authority. "You're not my dad," he would scream at teachers and coaches as a youngster when they reprimanded him.
Armstrong still maintains a significant, if dwindling, entourage, even as the mud sticks to him more than ever before. Many continue to support him, yet the International Cycling Union, the UCI, always so quick to defend him in the past, has been stunned into silence for much of the past week.
Within days of their training ride in Nice that summer, Hamilton and Armstrong flew off to compete in the 2000 Sydney Olympics. Both raced in the men's time trial. Armstrong took bronze, Hamilton finished 10th. And, in an all-star field, populated by many notorious names, none of the riders tested positive.
But then — despite the litany of police raids, confessions, whistle-blowers and allegations — not many cyclists failed a formal UCI doping control during the Armstrong years. Now, though, the dam has burst, and it feels as if everybody was doping, yet hardly anybody ever failed a test.
So why was that? Were the tests inadequate? Were the riders too clever for the testers? Were there cover-ups?
All of the above, Hamilton claims, in what is a damning indictment not just of Armstrong but of all those in positions of power who colluded or turned a blind eye.
By conceding on Friday that a doping amnesty may now be the only way out of this nightmare, current UCI president Pat McQuaid seemed to acknowledge the extent of the governing body's failure.
Hamilton and Coyle also claim that the UCI had effectively covered up a positive test from Armstrong at the Tour of Switzerland, and that Armstrong's infamous donations to the UCI — "like Al Capone buying police cars in Chicago," according to one commentator — were made in the aftermath.
It is known that Armstrong made two cash donations to UCI funds, one of $25,000 directly from his personal account, in 2002, the other of $100,000, from CSE, his management company, in 2005. At the time he claimed that they were to "combat doping".
Bizarrely, McQuaid has always denied that the donations, made during prior incumbent Hein Verbruggen's reign, represented a conflict of interest.
"What I don't like is this suggestion that Armstrong gets special treatment. Armstrong gets no special treatment, he gets the same treatment as everybody else," McQuaid said at the time.
But when the Texan made his comeback, in early 2009, the UCI did give Armstrong special treatment, bending their rules to allow him to compete, as he had not fulfilled the required anti-doping programme. Yet for all the revelations, the hypocrisy continues.
Tomorrow, it is likely that Alberto Contador, in his first race back since serving a doping ban, will win the Tour of Spain thanks to an extraordinary lone attack last week. As usual, the context is everything. Contador's manager Bjarne Riis doped to win the 1996 Tour de France, and according to Hamilton, facilitated doping practices.
Contador's solo attack on Wednesday last week, feted by many in cycling, was a throwback to the old days, a lone move of the kind not often seen in recent races.
"That's not realistic any more," Bradley Wiggins said of such attacks after his Tour win in July, before adding, "unless you have a couple of extra litres of blood."
Now cycling sits and waits for the final outcome of a torrid saga that began in July 1998, with the Festina Affair. For the pugilistic Armstrong, Hamilton, once his understudy — his quietly-spoken, well-mannered, dog-loving former team-mate — is an unlikely assassin.
But like Millar, the Bostonian has experienced a catharsis. The well of rage and self-loathing drawn out by Coyle could no longer be contained. "I feel fantastic," Hamilton said almost evangelically on American TV this week.
No doubt the witches' brew that fuelled cycling's Generation EPO — a lack of regulation, irresistible financial incentives, a complicit governing body and a fawning, unquestioning media — will one day come to the boil again. Perhaps this time, though, the painful lessons of the Legend of Lance will be remembered and professional sport will at last be ready to respond.
l Jeremy Whittle is the author of Bad Blood: the secret life of the Tour de France.