In many cases athletes are found to have consumed TMZ unintentionally, through contamination.

Valieva claimed her positive test result could have been caused by consuming food that had been prepared on a chopping board used by her grandfather to crush his pills.

However, the Court of Arbitration for Sport said they could not back up that claim with “any concrete evidence”.

Tennis world number two Swiatek tested positive for TMZ in a urine sample collected in August 2024.

She was provisionally suspended from 12 September before winning an appeal. Swiatek will now be eligible to play from 4 December 2024.

After an investigation, the International Tennis Integrity Agency (ITIA) accepted that the positive test was caused by the contamination of a regulated non-prescription medication, melatonin, which she was taking for jet lag and sleep issues.