Responding to questions from MPs, Brailsford divulged the package contained Fluimucil, a decongestant not included on a banned list of substances by anti-doping authorities.
“[Team doctor] Dr Freeman told me that it was Fluimucil that was in the package, a product that is for a nebuliser. That is what was in the package,” Brailsford told the culture, media and sport select committee.
The 52-year-old is credited with masterminding British Cycling’s Olympic gold rush and Team Sky’s four Tour de France victories, first of which was Bradley Wiggins' triumph in 2012.
Read more: Wiggins defended by team-mate over TUE row
Speculation has been rife since October when details were unearthed of the delivery of the package to Team Sky at the end of the Criterium du Dauphine to the Alpine ski station of La Toussuire.
What is Fluimucil?
According to the drug company's website, Fluimucil is an effective mucolytic which helps to get rid of sticky and thick mucus that is obstructing the airway, resulting in coughing.
It contains the active ingredient N-acetylcysteine, which is a precursor of Glutathione (GSH), and acts quickly to break down and expel phlegm to clear the airway.
Tell me why?
Brailsford had previously refused to shed light on questions about the package, delivered by the then manager of the British Cycling women’s elite team, Simon Cope.
And Team Sky sources told City A.M. the reason for Brailsford staying tight-lipped was because he didn’t want to prejudice any ongoing investigation by UK Anti-Doping (UKAD).
UKAD’s enquiries had been triggered by Brailsford when he had found out about the suspect package.
Let’s not forget, I was not aware of the package at the time.
It was the climax to a curious day of questioning where beforehand British Cycling bosses left MPs dumbfounded in dodging questions on what was in the suspect package after claiming UKAD had told them not to disclose details as the investigation was ongoing.
UK Anti-Doping give the sign-off for MPs to ask questions
Email to: Damian Collins MP, Chair, Culture, Media and Sport Committee from David Kenworthy, Chair, UK Anti-Doping, 18 December 2016.
Dear Mr Collins
Further to our recent conversation, this email confirms that UKAD has no objection to members of the Select Committee asking questions about matters that may be covered by UKAD’s investigation into cycling.
You will be aware from press coverage that the investigation is, in particular, centred on the delivery of a package.
Because of speculation surrounding this package it would be quite proper for the Committee to ask questions about this and any other aspect that the Committee considers relevant.
David Kenworthy, Chair, UK Anti-Doping
Even though MPs brandished a letter at the start of proceeding, sent to them by UKAD and giving the nod for them to ask attendees about the package, flustered bosses refused to budge.
It was only when Brailsford was questioned, over an hour later having had time to digest the 80-word letter, that mystery was finally solved.
UKAD is still yet to rule on the – now public – revelations by Brailsford.