The Olympics is often described as the biggest gender-equal sporting event in the world. And yet before sportswomen were even allowed to compete in weightlifting, boxing or wrestling at a Games, we had already witnessed our first female prime minister and a woman venturing into space.

On the eve of the 32nd Olympics, 125 years after women were banned from the first modern Games – founding member Pierre de Coubertin deeming their presence “impractical, uninteresting, unaesthetic and incorrect” – the International Olympic Committee is billing Tokyo 2020 as the first truly gender-balanced Games, where 48.8 per cent of competitors are female and where, it claims, “women and men have equal prominence”.

With the meteoric rise in profile of women’s sports, the outside world has changed, too. The likelihood is that globally established female athletes, such as Dina Asher-Smith, Shelley-Ann Fraser-Pryce, Naomi Osaka, Simone Biles and the star-studded American women’s football team will not only dominate the Olympic narrative like never before, they will leave previously blue-riband events such as the men’s 100 metres in their dust.

It will be a welcome moment but long overdue and one that Denise Lewis, Olympic heptathlon champion in 2000, believes women will grab with both hands.

“Things have changed so much, even from when I competed at my first Olympics,” Lewis says. “We are breaking down those barriers and proving when you get the opportunities, young girls will evolve and their expectations will increase, their application to training and their beliefs will all increase.”

Women’s Olympics Interactive timeline

Lewis remembers Sally Gunnell’s 400m hurdles gold in 1992 and the motivation she drew from seeing a female subsequently recognised and publicly acclaimed after an athletics era so long dominated by British males. “In the past, it was very much, let’s showcase the men’s 100m, that’s going to be the blue-riband event. I think attitudes are slowly changing, there is great competition going in the women’s event and that is really refreshing. I don’t think we should be apologetic about our female chances.”

The history of women’s involvement in sport and, by extension, the Olympics, has never been a straight path towards inclusion, rather a series of peaks and troughs.

“We have to see women’s sport within its wider context,” says Fiona Skillen, sports historian at Glasgow Caledonian University, who believes modern sport was defined by the hugely gendered values of the Victorian era. “The idea that men are strong and robust and mentally very astute. By contrast, women are  seen as having quite weak bodies and weak mental states.”

Four years after the inaugural Games in 1896, women were allowed to compete in Paris, albeit in sports seen as less physically demanding – sailing, equestrianism, croquet, tennis and golf. Yet they made up just 2.2 per cent of the total of 997 athletes. It would take until Helsinki 1952 for them to rise above 10 per cent.

Team GB historical gender split at Summer Olympics

“Participating in competitive sports, and aggressive sports in particular, really was a complete anathema to society’s ideals at the time,” adds Skillen. “They saw participation as being really dangerous because it could potentially stop a woman from producing children, perhaps becoming attractive.”

That is not to say women were taking their exclusion lying down. Women did participate in physical sport, such as sailing, football and mountaineering, but they were often in the minority and faced a backlash, particularly from male-led organisations. It is a well-worn path throughout Olympics history:

 In 1896, Greek athlete Stamati Revithi was refused entry to the marathon and ran by herself the following day. Women were finally allowed to run an Olympic marathon in 1984.

 The 1912 Games had no female American swimmers as they were not able to compete in events without long skirts, and British schoolgirl Helen Preece tried to enter the modern pentathlon but was refused. It would be another 88 years before women competed in this event.

 In 1928, more women were allowed in the Games, but the 800m was deemed too dangerous – a ban that was not lifted until 1960.

Then there are other sports that had to wait over a century for women to participate. Weightlifting achieved inclusion only 108 years after its male debut; for wrestling and boxing it was 104 years.

“The broad picture when it came to anything in a strength realm was that women just weren’t capable and it was unhealthy and detrimental to try,” says Judy Glenney, the American who helped put women’s weightlifting onto the Olympic programme in 2000.

It wasn’t until 1996 that the IOC amended the Olympic Charter, making one of its roles to “encourage and support the promotion of women in sport at all levels and in all structures, with a view to implementing the principle of equality of men and women”.

And ahead of this year’s Games, wording of the official Olympic oath to be taken at the opening ceremony has been tweaked as part of the gender-equality drive.

Complete breakdown of women’s participation at the summer Olympics since 1896

“We promise to take part in these Olympic Games, respecting and abiding by the rules and in the spirit of fair play, inclusion and equality,” the oath will include.

While Britain has competed at every summer Olympics, it is only in Tokyo that female athletes will outnumber male participants. The IOC is billing Tokyo as a “step forward” for gender equality. All countries are expected to have at least one female and one male athlete, and teams are encouraged to have a competitor from both genders carrying their flag at the opening ceremony.

Until now, just three British women have been a flag bearer – swimmer Anita Lonsbrough (Tokyo 1964), equestrian rider Lucinda Green (Los Angeles Games 1984) and judoka Kate Howey (Athens 2004). For Howey, the only British woman to have won two judo Olympic medals, it was a “massive achievement” to be voted for by her peers, but “as one of three women, proportionally it’s not great”. Head coach at British Judo, she is also tired of being viewed as an exception – and not the rule – when it comes to coaching.

“It’s important to have females recognised in their field at the Olympics,” says Howey, part of UK Sport’s female coaches leadership programme, which aims to more than double female representation in the Olympic and Paralympic high-performance community by Paris 2024. “For the youngsters, to see a female in any coaching role, and British female athletes outnumbering men, that’s immense.”

While the Tokyo participation data is encouraging, there are still so many areas to tackle to truly end the Olympics gender gap. Whether it is the shockingly low numbers of female coaches or the IOC policies that fail to recognise women athletes’ needs, Tokyo 2020 is a good starting point, but the challenge is far from over.