Olympic gold medalist Sun Yang faces a lifetime ban from swimming after a bizarre clash with anti-doping testers ended in the destruction of a sealed vial containing a blood sample.

Sun, from China, is the only swimmer to have won Olympic gold medals at 200m, 400m and 1500m freestyle.

After missing an out-of-competition test on September 4 last year, Sun, supported by Dr Ba Zhen — both with previous doping suspensions to their names — took what a panel of doping lawyers called a “huge and foolish gamble” on his “entire athletic career”, according to a hearing report.

The 27-year-old allegedly went on to break several testing protocols, and left the testing room unaccompanied to pass urine into the sample cup.

According to witnesses, the Olympian’s mother ordered one of the security guards to destroy a blood sample that was taken at the nearby clubhouse.

After skipping an out-of-competition drug test in September last year, doping lawyers said that Sun made a “huge and foolish gamble” on his “entire athletic career,” according to a hearing report.

Dr. Ba Zhen – who supports Sun – reportedly contacted Dr Han Zhaoqi, of the Zhejiang Anti-Doping Centre after the incident.

Han, who wasn’t present at the scene – reportedly told the panel at FINA (Fédération Internationale de Natation – International Federation of Swimming) that the nurse at Sun’s testing didn’t have the necessary paperwork.

The Times reported that “the panel accepted his word, stating in their report that they would “never know” the truth of that. And on January 3 the panel ruled in the swimmer’s favour.”