It was ideal fodder for a global media pile-on. Her column was picked up far and wide and transgender athletes were quick to respond, slamming Navratilova for being ill-informed and transphobic, a claim she refuted given her former coach and friend Renee Richards was one of the first athletes to identify as transgender.

Among the respondents was Canadian cyclist Rachel McKinnon, a World Masters champion, who transitioned in her late 20s. She called the comments "disturbing, upsetting, and deeply transphobic" and has been a staunch advocate of the rights of transgender athletes to compete within the rules set by the governing bodies of various sports.

Navratilova's tweet and the ensuring column weren't entirely out of left-field. There has been renewed debate about whether transgender athletes should be allowed to participate at elite levels of sport, what, if any, advantages they may have and under what guidelines they should compete.

In the UK, new voices have emerged. One of them is a group called 'Fair Play For Women', which describes itself as a "grassroots campaign group made up of ordinary women from all walks of life who have come together to fight for women’s and girls’ sex-based rights. We are a non-partisan collective of women, with no formal links to any particular political networks."

One of their new campaigns, launched in early February, aims to keep female sports free of transgender athletes until more evidence becomes available about fairness and the physical concerns of biological females that may be smaller and not as strong as transgender competitors.

Their spokesperson, Nicola Williams, claims she was 'uninvited' by the BBC to debate McKinnon on the issue in the wake of Navratilova's outspoken remarks. On Facebook, the group backed Navratilova's comments and compared the advantages gained by some transgender athletes to taking steroids. In turn, 'Fair Play for Women' has been criticised as inherently anti-transgender.

"Two important issues raised by Martina today 1) Current trans eligibility rule is not fit for purpose 2) Anyone raising concerns will face incredible backlash," the group posted on Twitter. "We are calling on sports policy leaders to work with us. Good evidence-based policy making is the solution. We can help.

"We don't let women train on performance enhancing steroids and then wash them out before competition. The same concept must apply to transwomen who wish to play sport. If not your policy will be unfairly discriminating against females."

The issue has been hugely topical closer to home in recent years. Hannah Mouncey was ruled ineligible for the 2017 AFLW draft after concerns about the size difference between her and her potential opponents.

She dismissed Navratilova's commentary when she spoke to the ABC earlier in the week: "That for me highlights that she doesn't know what she's talking about, and as a result there's no reason to listen to her."

The International Olympic Committee have policy around transgender athletes, including permitted testosterone levels. But those levels are likely to be halved by the time Tokyo begins, making it even harder for transgender athletes or female athletes with naturally high testosterone levels.

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That is a hot-button topic in athletics at the moment, with dual-Olympic 800m champion Caster Semenya challenging an IAAF rule that would require women with naturally elevated testosterone to lower their levels by medication before being allowed to compete in races from 400 metres to 1500m.

That would mean Semenya has to take daily medicine or change her pet distances to continue to compete. Should she be forced to lower her natural levels, which many believe is an advantage no different to being taller or heavier, it would likely decimate her career. It could be a case with seismic aftershocks through a wide range of sports looking for precedent.

Navratilova has chosen her camp. Expect the debate to grow even fiercer as the Tokyo Games approach and potential new cases emerge to test the IOC's guidelines, its humanitarian principles and the patience of those who believe it tips the balance of fair play.