Once upon a time, there was a little girl who wanted to be a wrestler. As a teenager, she wrote a school essay about her ambition, which she described as "something that I have to do." She began training when she was 18; within a decade her surprise arrival on one of the biggest stages was the highlight of the wrestling year.

Bayley is one of the most beloved NXT roster members in history. She appeared on the scene as a starstruck fan, with few genuine ambitions, merely happy to be there and unable to stop herself from hugging her heroes, everyone from Ric Flair to AJ Lee. Gradually, she realised that not everyone she encountered deserved a hug -- some of them were not good people, and they did not have good intentions; they were happy to take advantage of her good nature for their own benefit. Yet, with her hairband, her jaunty side ponytail, her garishly bright ring gear and her smile, she didn't grow embittered, or sly, just more determined to win the NXT women's championship.

And she did. She picked up the title at NXT Takeover: Brooklyn in August 2015, and as she celebrated, three other women congratulated her. One was her vanquished opponent, Sasha Banks; the other two were Charlotte, daughter of Ric Flair, and Becky Lynch, a flame-haired steampunk-inspired brawler. Together the quartet comprised the so-called Four Horsewomen of NXT -- the standard-bearers for women's wrestling in the division, showing that they could carry the entire brand should they be asked to, with their in-ring abilities, their personalities and their connection with the audience.

While three of the Four Horsewomen were a regular fixture of WWE's weekly television shows soon afterwards, Bayley stayed on NXT. She helped through a new cohort of female wrestlers, reliably eliciting a roar of delight from the crowd every time she appeared.

Finally, on Monday night, she triggered that same response from an even bigger crowd. She made her main roster debut on "Raw:"

The scrappy underdog isn't an unusual trope in wrestling -- Bayley's male equivalent would perhaps be Sami Zayn, fighting his way through injury to the men's title -- but it is unusual to make the conquering hero a woman, and even more unusual within WWE confines to present her without any streak of malice or malevolence.

Yet Bayley is a great person as well as a great wrestler. Maybe that's part of her appeal, and why even jaded, cynical wrestling fans will cheer for her and throw up their arms when the inflatable tube men spring to life at the top of the entrance ramp. Even the most hard-hearted individuals can't help but smile when they see someone who is revelling in being able to live their dream. The Rock famously recommended that new wrestlers seeking a character should simply take their own characteristics and ramp them up to the mythical 11. Bayley is a genuinely warm, good-hearted individual.

Sasha Banks said as much when the quartet of female NXT graduates spoke to GQ magazine, describing how the women had once been "competitive" in the locker room, viewing each other as rivals. That was before Bayley's arrival.

"She changed my mindset completely on how to give a helping hand," Banks said. But Bayley's kindness and openness isn't a recent development.

Rhia O'Reilly, Irish star of SHINE and SHIMMER, spent some time training with Bayley, then known as Davina Rose, around four years ago. She has been thrilled to see her friend's progress since then.

"She has an instantly likeable personality and we became friends very quickly," she recalls in an email.

O'Reilly has not been shocked to see her friend become probably the most beloved babyface in all of global wrestling.

"I think it's strange to see anyone you know become so well known and famous -- but it's not surprising," O'Reilly said. "She clearly has a natural talent for the business and is very passionate about what she does -- always has been. I've never met a person who didn't like her, in or out of the ring, so it's no surprise that the rest of the world loves her too!"

Wrestling writer Thomas Holzerman, however, was initially skeptical when WWE signed her; he had seen her on DVDs of shows and had not been impressed.

"She hadn't found herself in the ring and was on the same card as some of the best in the world," he remembers. "I remember being a bit perplexed when WWE signed her over the other elite women, but this was before the NXT/Performance Center track record was established. Glad I was proven wrong."

As Bayley has journeyed through NXT, she has taken the fans with her. Her likeability, her dedication -- and yes, her underdog spirit -- has them on her side. The explosion of noise that met her surprise appearance at July's Battleground, as Sasha Banks' tag-team partner, was the culmination of that.

More than that, it was the proof that NXT was no longer merely "developmental," a brand for novices to get more experience, one that wasn't marketable and wasn't watched by wrestling fans at large. Bayley had never been seen on actual television before that special event -- she was just a key part of WWE's web-exclusive Network content. And every single person in the audience knew who she was.

"I had no idea that was going to happen but I think we were all hoping it would!" O'Reilly said.

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"I was shocked because I had worked myself into believing Banks' partner would be someone underwhelming like Naomi -- nothing against Naomi, but she didn't have the cachet -- or, if it was a shock, that it'd be Nikki Bella [returning from a serious injury]," said Holzerman. "It was really heartwarming to see that the crowd knew who she was and cheered for her like a conquering hero. That made me believe that maybe more than just super nerds like myself watched NXT on the reg."

The one disappointment for Bayley and her fans was that this adrenaline-fuelled night, this celebration of her achievement and the progress of women's wrestling, was clearly billed as a one-off. Bayley and Sasha would not be a permanent tag team; nor would Bayley step up to become a focus of the women's division. Instead, she would return to NXT.

Bayley herself admitted that it felt a little frustrating to see her peers forge ahead of her; O'Reilly is sanguine about her friend's progress and recommends patience. She wondered whether someone as unique as Bayley may get lost in the main roster shuffle. Is it a possibility that someone who has built her NXT career path on being a fan of wrestling, on being generous, good-hearted, innocent and honest, simply might not work on the main roster -- where the women characters over the years have been duplicitous and over-emotional; sexualized, sexually aggressive and sexually harassed?

"Bayley is not the easiest wrestler to predict because she's such a unique character for WWE and has been kept in the chrysalis of NXT for so long," Holzerman said. "The main roster is still an unforgiving place for women. Bayley can get eaten alive -- but she can also break through and have crowds make WWE feature her in a positive way. If that happens, she can be the biggest superstar WWE has had since, well, John Cena at least. But that isn't certain at all, unfortunately."

O'Reilly is more confident that Bayley has the talent and the courage to remain herself and step into the brightest of spotlights -- and that her future will be even brighter than that.

"I think the reaction Bayley had at Battleground proves she can be the same person on the main roster," she says. "Even if she does have to adapt to be there, the core fundamentals of the superstar we know and love will always be there. And as for her future? It's whatever she wants it to be!"

At NXT Takeover: Brooklyn II, Bayley fought a valiant battle against champion Asuka, but was ultimately defeated. In the crowd to cheer her on were the other three Horsewomen, all of whom she hugged after the match. On her head she wore a hairband, design inspired by the ring gear Banks had worn in their title match the year before.

Banks was delighted with the compliment, tweeting: "She makes me feel special!"

Bayley replied: "Dude. You are."

So is Bayley.