The UCI referred to them, in deliberately sinister terms, only as the "men in black", adding that their suspicions centred on their possible use of illegal doping products. But most observers jumped to the same conclusion: the men in black were members of Astana, the team of this year's Tour favourite, Alexandre Vinokourov.

Adding to the air of suspicion, two Astana riders immediately found themselves involved in doping cases. Eddy Mazzoleni was put under investigation after finishing third in the Giro d'Italia; then Matthias Kessler, a stage winner in last year's Tour, tested positive, registering levels of testosterone that make those returned by Floyd Landis, during last year's Tour, look like a trace.

Then came arguably the most damaging revelation as Vinokourov confirmed that he has, since the end of 2005, been working with Dr Michele Ferrari. With his name invariably prefixed by "controversial" or "notorious" - or both - Ferrari is the Italian prepatori who trained Lance Armstrong until being convicted, in 2004, of sporting fraud and professional malpractice. These charges were later overturned on appeal but Ferrari was found guilty of prescribing banned substances to cyclists in the 1990s.

All of which means that Astana start the Tour as the most impressive and controversial squad. Whether or not they are the "men in black" is unclear - though the team reacted to the rumours by putting out a statement confirming that their riders sometimes train in plain clothing to avoid autograph-hunting "cyclo-tourists" on the Cote d'Azur, not UCI drugs testers.

Just as intriguing as the "men in black" story is how the Astana team came into being. It rose suddenly from the ashes of a major Spanish team, Liberty Seguros, whose sponsor pulled the plug prior to last year's Tour when it was revealed that its director, Manolo Saiz, had links to the Operacion Puerto doping scandal.

It was Vinokourov who sprang to the rescue. A national hero in his native Kazakhstan, the man universally known as "Vino" had a word with the country's then prime minister, Nursultan Nazabayev (now minister of defence and president of the national cycling federation). Within days a package had been put together, with Kazakhstan's five largest companies committing to an annual budget of €12m (£8m). The sponsors are mainly oil companies (Astana is the capital city of Kazakhstan). On the riders' shorts the branding is "Kazakhstan Railways".

The Astana strip is adapted from the country's flag: a washed-out, almost faded looking pale blue with a bright yellow sun shining out the lower part of the jersey, and a golden eagle flying beneath it. It's a colour scheme that seems to match Vino's personality - apart from the sun, that is. Though he has an attacking, aggressive style on the bike, off it, Vino is quiet and reserved to the point of being monosyllabic. He is easily caricatured as cold and dour. It is easy to imagine that he is not someone who will find Borat - Sacha Baron Cohen's Kazakh creation - even slightly amusing.

Astana were stopped in their tracks a year ago, just 24 hours before the start of the Tour. Having turned up in Strasbourg ready to race - and with the disgraced director Saiz having parted company - they became further embroiled in Operacion Puerto. Of the 13 riders excluded on the eve of the Grand Départ, five were from Astana. Vino was not one of them, but he paid the price. With Astana down to four riders, they were prevented from starting the Tour. The rules state that a team must start with a minimum of five starters. As Vino has since pointed out, three of those five riders were later cleared of any involvement in Puerto. He is still raging about last year's exclusion, saying that he spent last July "very depressed".

He didn't seem much happier during his pre-Tour press conference in London on Thursday. Neither did his right-hand man - and another contender for the Tour - Andreas Kloden, who skulked beneath a baseball cap. Most of the questions were directed at Vino and mainly they concerned Ferrari. "He's my physical trainer," said Vino. "I have worked hard. I have done nothing banned. I only work with him in training programmes. I work with the [Astana] doctors with questions of medicine.

"Lance Armstrong worked with [Ferrari] and won the Tour seven times, there was no problem," added Vino. "I just needed a better trainer, that's all. [But] when journalists hear the name Ferrari they think doping, doping, doping. It's not like that with him. I only work on training and he's the best there is. If I win this Tour, it will be magnificent and I will thank him."

Other questions hung in the air. There was Vino's many years with T-Mobile - whose doctors, it was revealed this year, were complicit in doping. Kloden was also at T-Mobile. So was Kessler, and Mazzoleni... Then there is Vino's friendship with Jan Ullrich, who has retired but whose links to Puerto have been proven.

And, of course, there is the suspicion that Vino and co are the "men in black". Astana's manager, Marc Biver, sought to put the record straight on Thursday. "We've had a bad week and we've suffered through a media persecution of the team," said an angry Biver. "There's been no respect for our team and no respect for our riders. I regret that certain insinuations by the UCI about 'men in black' that were directed toward us."