Monaco - Caster Semenya extended her winning 800m streak to 38 races, getting ever closer to Jarmila Kratochvilova's world record, but she's under increasing pressure to produce the goods given the rapidly approaching introduction of testosterone rules that could diminish her performances.
In Friday's high-quality Diamond League meet in Monaco, Semenya again delivered the type of race that promised to challenge the longest-standing individual world record in athletics.
Leading from gun to tape, the 27-year-old South African was in world record shape at 600 metres before fading down the home straight to eventually win in 1min 54.60sec.
"It was just fantastic!" beamed Semenya. "Only the last 100m were a little off for me.
"It was a long month of racing for me and now I need to rest. I feel that on my body."
Semenya added: "I wanted to break 1:54 but maybe next time. I want to be consistent at this level. I wasn't thinking about the world record and it wasn't on my mind."
Kratochvilova's record of 1:53.28 was set in 1983, the same year the then 32-year-old Czech runner won the world 400 and 800m double.
Her feats, coming relatively late on in a track career, allied with her incredibly muscular physique spawned allegations of doping, but she has always maintained her innocence and put her success down to the vitamin B12.
Semenya has spent her career also under the spotlight thanks to her success and physique.
The South African is currently challenging the IAAF over controversial new rules track and field's ruling body plan to introduce on November 1 on high testosterone levels in female athletes.
The double Olympic champion (2012, 2016) and three-time world champion (2009, 2011, 2017) is now unbeaten over the 800m since her elimination in the semi-finals of the 2015 worlds in Beijing.
But off the track, Semenya has turned to the Court of Arbitration for Sport (CAS) in her challenge of IAAF rules.
The powerfully-built Semenya is potentially the highest-profile female athlete that would be affected by such regulations.
Classified as "hyper-androgynous", athletes like Semenya would have to chemically lower their testosterone levels to be able to compete, something the 800m runner says is discriminatory and in violation of the IAAF's constitution and the Olympic Charter.
The IAAF's proposed rules have been welcomed by many female athletes as a way to create a fairer playing field, but there have been others who argue that it does discriminate.
Just last week the IAAF responded to an open letter from the Women's Sports Foundation and Athlete Ally, which requested that it rescind the new eligibility regulations for the female classification.
"The IAAF has not and will never try to prevent women from participating in athletics," the Monaco-based body maintained.
"In fact, the IAAF has been one of the foremost advocates for women's sport for almost a century. It has long championed equal access to competition and equal prize money at a time when many other sports still discriminate in this area.
"Contrary to claims made in an open letter written by the US-based Women's Sports Foundation, the IAAF's new female classification rule does not seek to prevent any woman from competing in athletics."
Under the regulations, "women with Differences of Sexual Development (DSD/intersex)" will be eligible to compete in distances from 400m up to one mile if they take measures to ensure their testosterone levels are on a par "with the rest of the female population".
"They will be eligible to compete in male and intersex competition. The choice is theirs," the IAAF added.
Semenya faces a battle at CAS to overturn the rules and perhaps a race to snatch Kratochvilova's world record to crown an outstanding career.