Sharron Davies
© Russell SachFormer Olympian Sharron Davies, photographed at her home in the West Country.
Sharron Davies was stopped by strangers in the street half a dozen times this week. The former Great Britain swimmer - she won a silver medal at the 1980 Moscow Olympics and two Commonwealth golds - is used to being recognised every now and then, but as she walked around Bath on Tuesday, the interactions were of a different kind.

"It was all parents who were just saying to me, 'Thank you. Thank you for speaking out on this,'" she recalls when we meet at her home near the city. "People didn't realise what was going on."

The debate Davies has been congratulated for partaking in is one that's slowly consumed women's sport for much of the past month: whether transgender competitors should be allowed to enter female competitions. It is a notoriously thorny and misunderstood issue, but it was inflamed three weeks ago when 18-time tennis Grand Slam singles champion Martina Navratilova wrote that it was "cheating" to allow transgender women to compete in female competitions because of the potential unfair physical advantages. Navratilova, accused at best of expressing herself clumsily and at worst of being deliberately transphobic, later apologised for using the word "cheat", but not before Athlete Ally - a US-based organisation that campaigns for LGBT sportspeople - cut ties with her.

Yet her view also had widespread support. Numerous other elite athletes (almost all of them ex-athletes, tellingly) such as Billie Jean King, Paula Radcliffe and Kelly Holmes, voiced their opinions on the matter, and generally expressed concern about what might happen if the issue isn't addressed in accordance with proper research and guidelines.

Davies has joined them, lending her weight to the pressure group Fair Play for Women and stating her position plainly: "I believe there is a fundamental difference between the binary sex you are born with and the gender you may identify as," she wrote. "To protect women's sport, those with a male sex advantage should not be able to compete in women's sport."

As well as receiving thanks, Davies, 56, has found herself having to defend that position - and herself - from attacks on Twitter over the past week. She too has been accused of bigotry and called a "terf" ("trans-exclusionary radical feminist", a common online slur), while Rachel McKinnon, a transgender cyclist who won a Masters Track World Championship title last year, called her a "transphobe" who was "sharing hate speech." McKinnon also posted a photograph of Davies and suggested "a lot of people would be calling her a man."

Cross-legged on the carpet in the relaxed confines of her living room, Davies doesn't appear to have any regrets about wading into the debate. Rather, she has a sheaf of handwritten, highlighted notes in front of her and a desire to be further understood.

"I've had as many people contact me who are transgender who understand, but there's this very militant, vigilant section of this group of people who hijack everything. [On Wednesday] morning on Twitter they had tagged all of Kelly Holmes's sponsor companies and told them how disgraceful it is they work with a transphobe." Davies says one Twitter user in Canada, where McKinnon is based, asked how much it would cost to send somebody to the UK to "create GBH."

"It doesn't bother me that she said I look like a man, I'm perfectly happy in my body and I have three children, that's all sticks and stones," Davies says, adding that "all I want is a debate. I have no problem with anybody who is transgender, I'm entirely open to people living as they wish to and empathise hugely, but that doesn't change the fact that I want fair sport for young women. We need to get people to understand and discuss the issues."

Hence Davies's notes, which serve as a reminder that beneath the vitriol from all sides, there is a serious matter that will have major implications for sportspeople everywhere - not least trans athletes.

Though none ever has, transgender athletes have effectively been permitted to compete in the Olympics since 2004, when IOC guidelines stated that competitors who transitioned from male to female or vice versa were required to have reassignment surgery, followed by at least two years of hormone therapy, in order to partake. Those guidelines lasted until 2016, when it was announced that surgery is no longer required, and that instead male-to-female transgender athletes need to show their testosterone level is below a certain point (female-to-male athletes have no such requirements) for at least a year before a Games.

"No surgery, no chemicals or oestrogen or anything, no diagnosis of gender dysphoria and just one year of suppressing testosterone, well, think of the abuse that could lead to - winning medals, college sponsorships, prize money..." says Davies, who, in her sporting career, regularly competed against East German swimmers who were later found to be doping with testosterone. "The benefits of being born a male give a residual benefit which will last forever. Michael Phelps has size 15 feet; your average female swimmer has size six. If someone is a good swimmer and they decide they want to transition to being a female, none of our girls would stand a chance."

It is a point that many scientists have supported: that at the highest level of performance, an elite individual born male would maintain distinct physiological advantages even after transition and suppressing testosterone. "There'd be a greater oxygen uptake capacity, longer limbs, probably greater strength, higher haemoglobin levels, all of which will give them a distinct advantage over the women they're competing against," John Brewer, Professor of Applied Sports Science at St Mary's University told the Today programme on Friday. Certainly there are examples around the world, such as Davies's singling out of Laurel Hubbard - a retired New Zealand weightlifter who set junior records before transitioning, then only lifted slightly less 20 years later, dominating female competitions - that give credence to such an argument, though such cases are rare.

"It has the potential to ruin women's sport. It's not anything to do with saying sport isn't for everybody, it's asking how we classify it. And rather than classifying it by gender, we have to classify it by sex. And if the transgender society aren't happy with that, we'll have to talk to governing bodies about an alternative, a transgender games or something. But how can this be fair to women?"

Davies admits far, far more research is needed. It is an area of sports science that is very much in its infancy and, as the trans movement makes such impressive strides for equality in other areas of society, the black-and-white world of sport is struggling to keep up, desperately attempting to keep both a level playing field and avoid excluding the trans community from competing. But she is adamant an open, safe dialogue to engage with scientific fact is crucial, too.

"If people in the trans community want to talk and meet for a coffee then I would love that, I have tried," says Davies, who admits she's never spoken to a trans athlete but will attempt to set up a forum of discussion soon. Looking back on the week, she is quiet for a moment, before putting her head in her hands.

"I pride myself on being fair, it has been such a big part of my life, trying to have fairness... I mean, I had bombs sent to me when I was with Derek, for God's sake," she says, referring to a letter bomb sent by Danish neo-Nazis to her and her second husband, the black athlete Derek Redmond, in 1997. "My daughter had to read those messages [this week]. I am not a bigot and I am not a transphobic. Why, because we in society see them as victims, are they allowed to abuse other people? It sometimes feels like the world has gone mad, and we've lost our common sense."

She gathers herself again.

"We all need to put our arms around each other a bit more and understand each other, where we're coming from and what we want to achieve. My argument is simple: that there is a benefit to being born a male, and that's not fair on females in sport. That's really it."