Suspicion gathered over one of Britain's much-decorated cyclists and took the shine off what ought to have been a bright day for the sport in the UK.
Rob Hayles, Olympic silver medalist and a world champion in 2005, was withdrawn from competition just hours before racing began at the track World Championships at his home velodrome in Manchester after he was found to have a haematocrit reading above the permitted levels.
A Dutch cyclist, Pim Ligthart, was also prevented from competing for the same reason.
The test measures the capacity of the blood to carry oxygen and was introduced by the International Cycling Union in 1997 in a bid to limit the use of the banned drug EPO. However, a high haematocrit level is not proof of EPO use.
And, on an evening when Bradley Wiggins collected his third World Championship gold in the individual pursuit and there was a silver in the team sprint, what was expected to be the first of five days celebrating British success became a pit of speculation.
The 35-year-old Hayles issued a statement on his website, saying he was "disappointed and frustrated" at having to miss the two weeks of competition mandatory to anyone with more red blood cells than is deemed healthy.
Blood which is too rich in the oxygen-carrying cells increases the risk of a stroke or heart attack as it is thicker and consequently harder to pump through the body.
Hayles told BBC Radio Five Live: "I would have to be an idiot to do something like that.
"It's most definitely something that hasn't happened - hand on heart."
And he was backed by Wiggins - in partnership with whom he won a bronze medal in the Madison at the Athens Olympics - after the Londoner had beaten Holland's Jenning Huizenga in the final of the pursuit.
Asked if he had any doubts about Hayles, Wiggins said: "Absolutely no doubts whatsoever."
He added: "People will jump to the worst case scenario but Rob is one of the longest serving guys on this programme and one of the cleanest guys around."
Hayles' suspension puts pressure on British Cycling's performance director, Dave Brailsford, who has nailed his reputation to establishing a drug-free environment in his team.
He has introduced an extensive internal testing system where riders are required to undergo blood monitoring and performance levels are also watched closely for any sudden or unexplained improvements.
Perhaps counting in his defence, Hayles' performances have not been exceptional recently - to the extent his place in the British team for the Olympics is understood to have been at risk.
And Brailsford said: "I have known Rob a long time and there has never been any doubt in my mind that he has been anything but a fantastic athlete for Britain.
"He does not take drugs."
Brailsford is putting his trust in further tests to exonerate Hayles, who has won three World Championship gold medals as well as a silver and two bronzes at two Olympic Games.
However, Brailsford, who has established Great Britain as the world's dominant force in track cycling and is making inroads in other disciplines, admitted to being dismayed by the news.
"You work so hard and put so much effort into being open and transparent but unfortunately these things can happen," he said.
"It's a massive distraction but this is where it's my job to manage."
The controversy did not seem to affect Wiggins who was confirmed as overwhelming favourite to win a second Olympic gold this August by winning his third pursuit title with a ride which was well within his comfort zone.
In the team sprint, a British trio of Chris Hoy, Jamie Staff and Ross Edgar lost out to France in the final but there was no shame in that as the winners set a new world record.
And the evening ended on a note of comedy just across the road from Manchester City's Eastlands stadium when The Marseillaise was cut off after the first few notes - a handful of French supporters provided a version from the stands while the overwhelmingly British crowd clapped along.
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