Cheryl is an Analyst at the Drug Control Centre, King’s College London.

The Drug Control Centre analyses human urine and blood samples for the presence of performance enhancing drugs. They use very sensitive techniques which can detect chemicals at very low levels.

Cheryl carries out the initial screens that look for, among other things, steroids, stimulants, diuretics and beta-blockers.

Cheryl says that her job "involves a thorough understanding of the chemistry theory behind the techniques we use."

She says it’s a challenge to keep up with the ever-expanding list of banned substances.