In the blue corner, the former British and European champion from Liverpool: Natasha Jonas. In the red corner, the five-time European champion, four-time world champion from Bray, near Dublin: Katie Taylor.

In the audience, a few thousand giddily cheerful fans, waving union flags in the way Britons have suddenly lost their self-consciousness in doing, alongside many more entirely unrestrained Irish supporters, flapping tricolours and bellowing with no self-consciousness whatsoever. The green corner, if you will.

Excel's South Arena 2 may have witnessed a small piece of history on Sunday, when the first ever  http://www.guardian.co.uk/sport/boxing" rel="nofollow - boxing  bout between two women was staged as part of the Olympics, but a day later it was host to another striking novelty – the first time in the London Games in which a British competitor has been out-cheered by her rival's supporters.

It was no reflection on Jonas, who is an impressive boxer and seems a thoroughly charming person; she had been roared to the rafters, in the now-traditional Team GB fashion, during her first 60kg bout on Sunday against the American Quanitta Underwood, crediting the crowd's support for a "second wind" that carried her to a comfortable win.

But Taylor is a phenomenon, a slight and softly spoken woman 1.65 metres tall (5ft 5in) who, once in gloves and a mouthguard, turns into a fighter of stunning ferocity and skill, and had experienced boxingcorrespondents making impressed mutters as they waited for the two fighters after the bout.

If women's boxing was inaugurated on Sunday, it arrived on Monday, when the gender of the fighters was the least interesting thing about their contest. The women's sport may have a low profile in Britain, but in http://www.guardian.co.uk/world/ireland" rel="nofollow - Ireland , Taylor is a superstar (she is also, in her free time, a member of the women's national football team), with an appeal way beyond boxing's traditional heartland. "Yes, she's fighting the English girl," a smartly dressed middle-aged Irishwoman said loudly into her mobile as she queued outside the arena centre for a latte. "Oh, of course we're going to shout and cheer her on like mad."

Ireland is good at boxing – it's by far its most successful Olympic sport, and John Joe Nevin is guaranteed at least a bronze at bantamweight in the men's competition, with a number of other fighters still in contention. But Taylor is very, very good at boxing, and it will be a huge upset if she fails to win gold.

To measure how significant this is for her country: Ireland, in its entire Olympic history, has won 23 medals in total, one more than Michael Phelps. The country's eight golds compare to the swimmer's 18. Another would be welcome indeed.

The Ryan family had come from county Laois, all eight of them, three generations, just to see Katie. Daughter Finn, in tricolour wig, Irish cap and facepaint and wearing a T-shirt reading: "You'll never beat the Irish," said none of them had had any interest in boxing, or even, particularly, in the Irish football team, "but we started following Katie, so we're educating ourselves". Why the appeal? "She's just a lovely girl," chipped in her mother. "When you think of women's boxing, she's not what you think of. She's feminine."

There were other contests of note on Monday: chief among them a bout between Tunisia's Maroura Rahali and Mary Kom of India, a mother of two and a superstar in her own country who has won the world championships five times at 45-48kg.

Because that weight is not being contested in London – only three women's weight divisions having been admitted to the Olympics bill compared to 11 for men – the 1.57-metre-tall (5ft 2in) Kom has had to bulk up to fight at flyweight against fighters much bigger than her. She won comfortably, 15-6, however, and will contest the semi-finals on Wednesday.

Britain's Nicola Adams also won her bout against the Bulgarian Stoyka Petrova in the same division, but Savannah Marshall was defeated by the Kazakh fighter Marina Volnova in the heaviest 75kg category.

There was no question, however, which was the main event. The Irish bellows of "Ole! Ole! Ole! Ole!" had begun before the first two-minute round was done; shortly into the second, all commentary was lost beneath The Fields of Athenry. Jonas put up gallant resistance but was no match for Taylor's blistering punch rate and accuracy.

As the Irishwoman closed the final round, taking the bout 26-15, the crowd leaped to their feet, embraced and the songs began again, while a number headed straight to the concession stalls. Jonas took it all in good cheer. "Being a scouser I'm used to noises like that. And what a way to get behind women's boxing."

It's a curiosity of the competition that, having received a bye for the first round, Taylor is already guaranteed at least a bronze medal after only one fight, as both semi-final losers receive the award. Was she relieved to have got a medal? "Not really. I'm going for a gold and nothing else. Nobody's happy with a bronze."

It was a "privilege", she said, to fight in front of a crowd that was quite so dementedly behind her, but also to represent her sport, and not only as a pioneer. "People didn't really realise the standard of women's boxing. I think we're shocking the world here this week."