Team Sky were probably hoping for a fresh start in 2018, a chance to wipe the slate clean and let talk of Jiffy bags and negligent record-keeping fade away. Those hopes were extinguished on Wednesday morning with the revelation that Chris Froome, the man around whom their recent years of dominance have been built, had provided a drugs test notching twice the regulated limit in the midst of one of his most cherished victories.

The B sample corroborated what the A sample had found: that Froome had the asthma drug Salbutamol in his system at levels of 2,000 nanogram per millilitre, double that allowed by the World Anti-Doping Agency, immediately after stage 18 of the Vuelta a Espana.

It is a potentially catastrophic blow to Team Sky, whose self-heralded commitment to transparency and clean riding was seriously questioned during Ukad’s 14-month investigation into what exactly had been delivered to Bradley Wiggins at the 2011 Criterium de Dauphine, despite the case eventually being dropped. It will be extremely difficult to continue should their winner of five Grand Tour triumphs eventually be punished.

Froome, a man whose achievements have so often been greeted with an unjustified scepticism, could now be stripped of the 2017 Vuelta and face a ban of up to two years from the sport. That scepticism is quickly intensifying and a career built in the face of constant questions over his integrity is in danger of forever being tarnished.

It is a first in Froome’s career and it should be stressed that this was not a positive finding of a performance-enhancing drug, but an adverse sample of a ‘specified substance’ which the sport’s governing body, the UCI, includes on a list of drugs allowed within prescribed limits. Froome does not face an automatic ban but in these cases the UCI makes clear that the emphasis is on the athlete to prove his innocence – namely that he did not take more than the equivalent of 16 puffs of his inhaler in a 24-hour period.

So begins a complicated blame game. Amid a series of revealing statements from the team’s camp, Sir Dave Brailsford highlighted Sky’s defence when he raised the “complex medical and physiological issues” around the secretion of Salbutamol. Team Sky entitled their own statement “Chris Froome responds...” and appeared to discuss their star rider as a entirely separate entity to the team, while Froome himself pointedly said that he “followed the team doctor’s advice” in increasing his dosage after feeling his asthma worsen.

Chris Froome could be banned after a possible violation (Getty)

The best case scenario for Froome now is that Team Sky prove the abnormal test result was somehow the consequence of a routine dosage, clearing him of any wrongdoing and leaving him free to race the Giro d’Italia and Tour de France in 2018 as planned. This was the route attempted by the Italian rider Diego Ulissi following his adverse sample (1920 ng/ml) in 2014, the most recent similar case. He underwent specially devised tests in Switzerland to recreate the conditions but could not recreate the results and was handed a nine-month ban.

The irony is that there is little evidence to suggest Salbutamol improves the performance of elite athletes. The rules are debated but they are there, rules which Froome admitted in his statement that he was well aware of, and rules which now threaten to leave a black mark on his array of achievements.

On the creation of Team Sky in 2009, Brailsford said: “We have thought very carefully about the criteria we are looking for, how we will screen the riders. We will have a very clear screening and selection strategy. There will be no riders who have failed drugs tests.” But during Sky’s early years of success Brailsford also stressed a strategy of marginal gains – small ways to get an edge over opponents, like optimising sleep by bringing riders personalised bedding to each hotel and employing a chef to measure out food intake to the minutest detail.

There has never been evidence of Brailsford masterminding a drug programme akin to Lance Armstrong’s Postal Service Team, but each passing controversy raises the question of whether clean riding and marginal gains are two mantras which can coexist in a sport with so many fine lines and grey areas. It is hardly a good look that a team so insistent upon their clean image should have this failed test revealed by a joint investigation between The Guardian and Le Monde, almost three months after they themselves were alerted on 20 September.

It is a hugely damaging blow to cycling as a whole. Froome may eventually be found innocent of wrongdoing but that will do little for a sport always reeling from the last punch when the next one connects. Imagine the UCI president, David Lappartient, receiving the news in September, days after being emphatically elected as the sport’s new head and hailing a bold new era. He would have hoped for Froome’s Tour de France dominance to be challenged, just not like this.