Anderson Silva, as famous in his native Brazil as Pele, drops his fists, sticks out his chin and goads his young American challenger, Chris Weidman, to take a swing. It's showmanship at its brashest, it's impudent and it's disrespectful. This is the Ultimate Fighting Championship (UFC) in the MGM Grand Arena, Las Vegas – and the crowd is lapping it up.

Sadly for Silva, and for his army of adoring, Brazil-flag-waving fans who have travelled to Nevada to cheer him on, his 38-year-old reactions let him down and the younger Weidman lands a punch square on the belt-holder's jutting jaw. The crack can be heard above the din and Silva falls like an oak – knocked clean out. But that's not the end of it: Weidman jumps on to his unconscious opponent and lands two more blows before the referee steps in.

The Brazilian half of the crowd falls silent in disbelief. Silva had been hitherto unbeaten, the "Mike Tyson of our sport right now", as Dana White, the president of UFC, described him before the bout.

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The home contingent, however, is going crazy: UFC has a new champion and hero. Weidman has just become box-office gold.

UFC is the biggest proponent of mixed martial arts (MMA) in the world. Created in 1993 with the goal of determining which is the most effective martial art – boxing, jiu-jitsu, kick-boxing, wrestling, karate, even sumo – UFC stages its bouts in an octagon-shaped cage so that fighters can use the fences to facilitate their moves.

In its infancy, it marketed itself with the tagline "There are no rules", and its violent nature drew much criticism. Labelled "human cock-fighting" by the American senator John McCain, it was regarded as an underground movement. "When I first saw it, I thought it was bit crazy," Norman Parke, a UFC fighter from Northern Ireland (and one of 16 from the UK and Ireland in the sport) tells me in Vegas the day before his bout. "I thought, 'I don't want to be doing this.'"

At first, anything (except biting, eye-gouging and groin strikes) was allowed in the ring, but over time, and as UFC has fought to gain acceptance across America and overseas, the rules have evolved (it now has 32) and it has sought to shed the worst of the "cage-fighting" connotations. Head-butting, groin strikes, kicking an opponent in the head when they are down, all have been outlawed, while open-fingered gloves are now mandatory, to reduce injury.

With these changes, and the sport's emergence into the mainstream, standards have strengthened, its popularity has soared, and the purses for fights have improved. If a combatant is to be successful, they now need a combination of martial arts in their armoury rather than relying on one. To this end, fighters are allowed up to 10 coaches to teach them different techniques. The route taken by Parke, a 26-year-old from County Antrim now targeting a title fight, is typical of most fighters in UFC: as an Irish freestyle wrestling champion, he was a specialist in one of k the disciplines required, then learnt other skills on moving to the States to take up MMA.

Tickets for fights are snapped up instantly in the US. At the MGM Grand for the Silva-Weidman fight, just over 10,000 were sold at prices ranging from $125 in the gods to $1,200 in the VIP areas, bringing in gate receipts of just under $5m. Bouts are also shown on pay-per-view for $60 a night, after a seven-year, $100m deal was secured with Fox TV last year.

Which all means it's big business. Big business indeed. UFC claims to be the world's fastest-growing sport, which is no small brag: broadcast to nearly 800 million households in 28 different languages in more than 145 countries, it is already the world's biggest pay-per-view event provider. Popular across the US and South America, UFC sees the Japanese market as potentially lucrative, and expects to expand ever more into the UK, where many fight nights have already been staged at venues such as the O2 – where it sold out – and the MEN Arena. BT Sport, the new channel that launched on 1 August, will dedicate a weekly magazine programme to the sport, as well as presenting live action.

"I've been working on increasing UFC's exposure in the UK since 2002," says White, the 43-year-old straight-talking American entrepreneur behind the movement. "It's a very important market to us. We are definitely fighting the fight there – and every other country."

Garry Cook, the former Manchester City Football Club chief executive, is head of spreading the UFC word across Europe and its next stop in this country is Manchester, in October. "UFC is a pure product," Cook told The Independent earlier this year. "We have an audience, drama, unpredictability. No one is pretending to the consumer."

This is where the sport differs from WWE, the fake wrestling so popular across the US. The athleticism required in MMA is immense. "I'm more of an athlete than a lot of professional athletes," says the American fighter Cub Swanson, who credits the disciplines he's learnt through MMA with saving his life, after he spent his youth drifting in and out of various juvenile detention centres. "It's in the way I diet, the training I do, the way I conduct myself." The action is real, unscripted and brutal as a result. Rounds are a shattering five minutes long and there are five of them in a title fight, with three in bouts on the undercard. There is also razzmatazz aplenty, hype, hyperbole and ring girls between rounds.

The UFC marketing machine is well-oiled and moving in the right direction. And its exponents believe boxing could learn a thing or two from this upstart sport, not just in terms of glamour, but in action, too. There is none of the avoidance between leading protagonists that dogs boxing, because White controls who, of his 400 fighters across the globe, fights who. He also monitors the quality of the bouts closely so that fans get value for money. Thus, the best k fighters meet in the title bouts because White arranges it that way. There are eight weight divisions, categories familiar to boxing fans, and most nights finish with a title fight – failing that, it will be a local fighter of interest or a headline act.

"People have a lot of options for things to do on a Saturday night," says White. "If we get a show with a bunch of guys who just want to stand there and push up against the fence for 15 minutes and try to squeak out a win, how many people are going to want to tune in the next Saturday night? And if that keeps continuing, you become boxing, where guys are running around in circles and nobody fights. And the fan walks away going, 'That fight sucked.'"

While boxing figures in this country are growing in terms of participation and viewing, the former welterweight champion Ricky Hatton is on record as saying that his sport needs to be wary of UFC and its high entertainment value.

The level of entertainment is no mere serendipity: to ensure each minute of each round of each bout is exciting, UFC fighters get bonuses for finishing a fight early. "It's a huge incentive," says Cub Swanson. "It can be more than we make from the actual fight, and it gives the fans the sort of fight they want to see; we go for it.

"It's a more complete sport than boxing," he adds. "If you're talking about just hands, boxers are the masters, but fighting? That's MMA."

"It's a better spectator sport than boxing," agrees Mark Munoz, another American fighter, "because there are a lot more ways to win and a lot more action. It's exciting to see what techniques people will bring out: Superman punches, flying kicks off the fence, flying upper-cuts. That's exciting! Spectators love that."

Although cagey about the exact sums fighters take home, UFC states that it has made 10 millionaires. And as Weidman pointed out before his title fight, "Win on Saturday night and it will be a life-changer for me and my family." He reportedly earnt $50,000 for his victory and – other than superstar Silva, who earnt $600,000 that night, despite his defeat – the rest of the fighters on the Vegas card made between $10,000 and $90,000, depending on who they beat and how they beat them. Of course, that pales against boxing (undefeated in 44 fights, Floyd Mayweather Jr has made more millionaires with the purses he's paid to boxers he's beaten), but it's not to be sniffed at for one night's work.

Despite the surge in popularity and profile, however, UFC remains controversial in some quarters, and it is not yet accepted in every state: it remains banned, for instance, in New York. This is, perhaps, understandable: while not necessarily a desirable spectacle, bending limbs until there is a submission is commonplace. But perhaps the most contentious element is choking – cutting off the air supply to the brain until an opponent taps in submission, or simply passes out, whereupon the grip is released, the oxygen returns and the fighter regains consciousness. "Some guys don't tap out because they don't know where their pride is," says Parke. "You just go really light-headed, pass out and then… pop, you come back round again. But it's part of the game. It's a way to win." The "ground and pound" technique, which sees a fighter trap another's arms on the canvas and then land a succession of punches, has also been criticised.

But White dismisses such concerns. "One little thing happens and everyone wants to ban this, ban that. I don't want to get too political," he adds, "but it's like when something horrible happens with guns and everyone's like, 'Let's get rid of guns.' Then Boston [the bombings at the marathon] happens. No guns involved. If people want to hurt each other, they'll find a way. People like to label something and attack it."

Roger Gracie, a Brazilian jiu-jitsu fighter based in England, is insistent that MMA is less dangerous than rugby union or American football, and to date the worst injury suffered by a UFC fighter is a broken leg. "In MMA, you get cuts and bruises and a black eye, but they heal. It's superficial. Look at how many injuries rugby players and [American] football players have. They run and bang heads. That can cause brain damage. Their bodies are a mess. Look at rugby players' faces, their ears…"

"People who don't know about MMA say it's barbaric," adds Parke. "They think we're a bunch of animals. A bunch of hillbillies. I've been in this game 10 years and I find that really disrespectful. We are professional athletes and this is going to be the number-one sport in the world."

That's debatable – what's not is that the UFC bandwagon will roll on, spreading the hoopla and the hype, packing the punches and, perhaps most importantly, packing them in.

For ticket details for UFC in Manchester in October, visit ufc.com