Sitting opposite me in a small, wood-panelled office in his house in the posh suburbs of Mexico City is the country's most famous lucha libre wrestler, El Hijo del Santo. He is behind an expensive-looking desk, dressed in a smart suit and white shirt. He looks every inch the successful businessman - but his head is completely encased in a silver mask.

The phenomenon that is lucha libre is about to hit London when, on July 4, a clutch of top luchadores - including El Santo - comes to the Roundhouse. The sport involves men, often wearing masks and capes, wrestling each other mano-a-mano or in teams of up to four. Sometimes they dress as women and often there are dwarfs involved. It is Mexico's biggest sport after football.

Literally translated, lucha libre means “free wrestling”, but it is more like a choreographed circus performance as hefty men launch themselves at each other, tumbling around as they try to score points by pinning their opponent to the floor.

To say El Santo is a living legend is no exaggeration. The day before we met he had been given the honour of appearing on a set of Mexican postage stamps - the only sportsman (with the exception of the national football team) ever to do so. Sitting with us, his wife and manager Gabriela Obregón says: “It was an incredible honour. It means a lot of responsibility to him and great satisfaction.”

El Santo, who speaks no English, nevertheless seems to understand her. His masked head turns slowly on his thigh-thick neck towards me and he probably smiles. He is the second El Santo to don the silver mask. The first was his father (El Hijo del Santo means Son of Santo). El Santo Sr was among the original luchadores and the first to become a megastar. He starred in his own comic books and movies and attained iconic status. That's a lot of pressure for junior. “My father was No1,” he says. “I not be No2. It involves a lot of work. I have to be the best and it is lots of pressure.”

Later Gabriela takes me upstairs to El Santo's lair and shows me what can only be described as a shrine to his late father (he died in 1984). A mannequin dressed in the old man's fighting gear stands proudly over the masks of his vanquished foes. Posters adorn the wall. Personal effects still remain in the drawers in which he left them. It is a little unnerving. “My husband was the only one of five brothers who his father allowed to wrestle,” she says.

Back downstairs I ask El Santo what it is about lucha libre that so appeals to Mexicans. A growling voice comes from deep behind the mask, the steely blue eyes fixing on me.

“The magic,” he says. “It is part of being a sport, a spectacle. It is attractive to people because of the masks and the dress and the colours. It is part of the culture, like the mariachi and chilli.” Chilli? “They are symbols of Mexico and Santos is a symbol of Mexico.”

You are like a superhero, then. “El Santo is a superhero, but flesh,” he growls.

Like his father, El Santo is an exception among the luchadores. He has his own clothing and jewellery ranges. He earns a lot of money. He lives in the most exclusive neighbourhood. For others the story can be very different.

Accompanied by Octavio Rivero, the 28-year-old entrepreneur responsible for bringing lucha libre to London, I attend a fight at the Arena Naulcapan, the third largest venue in the city. I had imagined something along the lines of White Hart Lane, the third largest football stadium in London. Instead, it was more like Barnet's home ground.

A standard wrestling ring sits in the middle of the ramshackle arena. Seating is a series of concrete steps around the edge and some folding chairs in the “stalls”. It feels as if there should be chickens running around. It can hold about 4,000 people - tonight it is about a quarter full. But they make up in noise and excitement what they lack in numbers. They are all ages - dads with babes in arms, elderly women and young couples on dates.

Backstage it is all cast concrete and rain-stained walls. Next to the changing rooms is a Roman Catholic shrine featuring a particularly bloody painting of Christ. Nearly all the fighters cross themselves before going into the ring. The fighters tonight are semi-pros who have day jobs and are just starting out. They fight several times a week, trying to break into the big league. Only around one in ten ever does.

Out in the arena, two brothers, Trauma I and II, are in a tag team match with a pair of cross-dressing wrestlers. It seems never-ending. Suddenly, though, there's a commotion. Out of the crowd runs a dwarf. He tumbles into the ring, starts running around kicking shins and receives a thorough beating.

The crowd loves it, chanting, tooting horns, cheering on the good guys (the Técnicos), booing the bad guys (the Rudos). It's pantomime - violent, sweaty pantomime in which the Ugly Sisters beat up one of the seven dwarfs, but pantomime none the less.

The next day we meet Silver King, another London-bound fighter who played Jack Black's nemesis in Hollywood's recent take on the sport, Nacho Libre. Formerly an independent luchador unattached to any of the three major leagues, he has just signed to the top one, the Asistencia Asesoria y Administración. He looks like a big shaved bear. “In Mexico, if you are not on TV your rating goes down,” he says. “The top two companies have shows on national channels."

Silver King earns about £2,000 to £2,500 a week (the average Mexican earns £1,000 a month). “When I started in this business I didn't think I would be famous or get women or money,” he says, contented nonetheless that he got the full package.

He is certainly successful. He is the holder of a string of domestic titles and is a hit in Japan, where lucha libre is also phenomenally popular. That is where the real money is to made.

I find it strange that there are “titles”. Having seen a fight, it looked as staged as the sport's British equivalent, if more spectacular. This is a question to which neither he nor El Santo will give a straight answer.

“About 80 per cent of people believe that it is real,” Silver King says. “But even if you say it is a performance or a circus or entertainment you still have accidents and some people die. In ten years maybe ten guys have died, and people get brain damage.”

A Rudos in the ring, he sees it as his job to wind up the crowd. He has been stabbed in the leg and bottled for his troubles by overexuberant punters.

The next night, at a match organised by the second-biggest league, the Consejo Mundial de Lucha Libre, violence spills out of the ring again. Silver King's brother, a Técnico called Dr Wagner, and his team of two other fighters win a spectacular fight against three Rudos.

Before Dr Wagner can celebrate, however, his team inexplicably turns on him, pummelling him to the ground. Another masked luchador enters the ring and unmasks him - the most disrespectful thing that can happen.

The crowd explodes, hurling beer cans into the ring. I fear a riot, but then notice that they are cheering, hugging each other. “Will the fighters have arranged that?” I ask Rivero.

“Oh yes,” he grins.

Back at El Santo's mountain hideaway, and bearing this in mind, I repeat the question about matches being staged. “They really hit at me. This is real blood,” he insists. “But that doesn't mean it is a massacre. It is a sport. It is a competition. It has rules. But it is real.”

What does Gabriela think of all this blood and masked men wrestling in tight shiny costumes, I wonder. She pauses. “I think it's kinky,” she says.

Lucha Libre London, Roundhouse, NW1 (0844 482 8008), July 4-6

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