As Cassandro climbs the stairs, post-match, to the darkened balcony above the wrestling ring, his huge smile precedes him: it’s irrepressible; almost incandescent.

“I just bought my teeth for the third time,” says the Mexican wrestling star and NWA world welterweight champion, showing off his new, perfect gnashers. Because they were knocked out, you mean?

“Yeah, three times now,” he says. This, it transpires, is the least of a long list of injuries.

“I’ve had four surgeries,” he says. “I just had the last one 12 weeks ago on my knee, to remove a plate with eight pins.” Cassandro has suffered torn cruciate ligaments – anterior and posterior – in both knees, as well as a left tibia fracture. His right shoulder is on its fifth dislocation. This litany is a reminder that even if the punches are pulled, the falls rehearsed and the outcomes of matches predetermined, the stakes are still extremely high. “You can say it’s fake,” says Cassandro. “People say it’s choreographed. You can say whatever you can say, but when the body gives up, the body gives up.”

The Resistance gallery, where Cassandro has just wrestled, occupies the space under a railway arch in Bethnal Green, in east London. It’s the home of the London School of Lucha Libre, founded four years ago by former wrestlers Garry Vanderhorne and Greg Burridge. As well as putting on regular Friday night shows here, they teach a hybridised version of lucha libre (“free wrestling”), combining the traditions of Mexican professional wrestling – masked opponents, high-flying moves and soap operatic storylines – with a British sensibility. For the luchadors of Bethnal Green, Cassandro is a cross between mentor and patron saint; Vanderhorne refers to him as their “spiritual mamasita”. He trains students when he’s in town, and serves as an inspiration.

“I love London,” says Cassandro. “This is like my crash place. After I finish a tour, this is where I come.” In a recent New Yorker profile Cassandro maintained that his only complaint about Britain was that everyone here kept referring to him as a transvestite instead of a drag queen.

Facebook Twitter Pinterest ‘Cassandro is not somebody to play around with’ ... in action at the Resistance gallery in Bethnal Green, east London. Photograph: Frantzesco Kangaris for the Guardian

“They just can’t get to the word exotico,” he says, referring to the class of luchador to which he belongs, a type of character that first emerged in Mexican wrestling in the 1940s. Luchadors are divided into tecnicos (good guys) and rudos (bad guys); from the beginning, the exoticos – who were defiantly effeminate and fought in drag – were bad guys.

“They were rudos because they were like the clowns in the circus,” says Cassandro. “They were there to make people laugh. They weren’t really gay, unless they were in the closet.”

Nowadays Cassandro refers to the exotico as a wrestling “gender”. “We’re not transvestites, because I don’t do this out of the ring,” he says, indicating his made-up face. “I don’t do drag or anything like that. I don’t live as a woman. I’m gay, that’s it.”

Cassandro is actually American. He was born Saul Armendariz in El Paso, Texas, just over the border from Ciudad Juarez, Mexico. It’s a culturally fluid part of the world – young Saul spent most of his free time on the Mexican side of the river, watching lucha libre matches.

Neither side of the bridge was a great place to grow up gay. Saul quit school at 15 and apprenticed himself to a lucha libre trainer in Juarez. The first character he inhabited in the ring was a rudo called Mister Romano. Another luchador encouraged him to rebrand as an exotico, and eventually he came upon the persona of Cassandro, christened in honour of a Tijuana brothel-keeper called Cassandra.

Exoticos serve as comic relief, but also as targets for abuse. What we might term hate speech was, in the lucha libre environment, normal audience participation.

Facebook Twitter Pinterest Cassandro and teammates celebrate victory. Photograph: Frantzesco Kangaris for the Guardian

“Lucha libre in Mexico is like a religion,” says Cassandro, “and Mexico is a very machista country. Homophobia is everywhere.” Wrestling matches serve as pressure valves for the frustrated working poor. “It’s like a free therapy session for them,” he says. “They will go and scream their lungs out, and all the anger about what’s been done to them during the week, they get it out on the exoticos.”

Things have changed markedly, however, in the 26 years that Cassandro has been on the professional circuit. “Nowadays a lot of the fans that really know about lucha libre, they know that some of us – not all of us – have really dignified, with our skills and talent, our gender, the exoticos. Yeah, we are gay, but we do know how to wrestle.”

He can’t help it if some newer exoticos are undermining what he and others have built up. “People know,” he says. “They know Cassandro at least. They know Cassandro is not somebody to play around with. They know if they pay for a ticket, they’re gonna see Cassandro work his ass.”

There are a number of bouts on the undercard this afternoon, some between professionals, others in which students are making their debuts. The first is a three-on-three tag team event featuring a masked wrestler called Subject 265, who is said to be the product of several brain experiments gone wrong. Vanderhorne tells me that although lucha libre is classed as a sport in Mexico, he thinks of the British version as performance art, theatrical and full of knowing humour. It doesn’t look any less punishing for it. Lucha libre is known for being more acrobatic and more aerial than its WWE counterpart. Luchadors leap from the top rope to deliver flying kicks; they often tumble out of the ring and into the crowd.

The Resistance gallery is small; the ring takes up almost half the available floor space. The front row seats are largely taken up by small children. The second match is a female tag team bout – Psycho Badgers v Unicorn Power. Among the Psycho Badgers is a squid-masked villain called Senorita Pulpa. She leans on the ropes and snarls at the children. The children scream back, delighted.

Sexual and ethnic stereotypes are played up. One of the luchadoras, Psycho Lolita, is dressed as a schoolgirl. “She’s only 14,” says the announcer, “but she’s been wrestling for 15 years!” A luchador called Malik performs as the Asian Adonis (“He’s like a caramel Action Man!” says his manager, a character known as Jack Hammer). The fortunes of wrestlers change several time during a typical match. They spend a lot of time pretending to be badly hurt when they’re not and, one imagines, a fair bit of time pretending not to be hurt when they are.

When the time for the main event finally arrives, Cassandro makes his entrance with I Will Survive playing over the speakers. He strides through the audience wearing a cape with a 4ft train, beaming and chewing gum, his sleeveless top cut almost to the navel. Up close he is tiny – just 5ft 5in in his shoes.

Cassandro is facing three local rudos (these days, more often than not, the exoticos are the good guys), and is teamed with another celebrated Mexican luchador, Diva Salvaje, and a young newcomer called Cassius, who enters the ring with a lollipop sticking out of his mouth.

As soon as the bell goes it becomes clear the wrestling will be of a different order: Cassandro flips himself into the ring over the top rope. He slams larger opponents on to their backs and folds them up into neat packets. As he launches himself off the ropes for yet another airborne collision, it’s easy to see the skill – and the discipline – that goes into lucha libre. It’s also easy to see how he got through three sets of teeth in 26 years.

For a reigning champ, Cassandro spends a lot of the match on the mat, nearly getting pinned several times, but he rallies toward the end. At the climax of the bout he climbs up on to the top rope, and from there on to the balcony above the ring, clinging to the railings where the stage lighting was fixed (“I was burning my ass with those damn lights!” he says later). From this position he dives on to two opponents, taking them both down. He emerges unscathed, radiating joy as his team are declared the winners.

Later, however, he admits to being in considerable pain. “Yeah, my knees are killing me, and my shoulder,” he says.

The toll lucha libre has taken on Cassandro is not merely physical. From the beginning he battled addiction and depression. He attempted suicide before his 21st birthday.

“Wrestling has been the worst thing that ever happened to me,” he says, “because I had to discover first who I was not, and that I discovered in wrestling, through the drugs, the alcohol, the sex, the craziness back stage – just to be hard enough, just to prove to people that you deserve to be a wrestler.”

He has been sober since 4 June 2003 – the date is tattooed on his back – and has since come to find wrestling redemptive. He describes pain as a great motivator that helps him control his PMS. “Poor Me Syndrome,” he says. “I use the pain – it already hurts, now what are you gonna do about it? Either stay in the solution or stay in the problem.”

He maintains that his real opponent in the ring these days is his alter ego, Cassandro. “That ego is not my amigo,” he says. “Because, you know, Cassandro is the one who is trying to kill me. And Saul is now the one who’s in charge and is trying to heal Cassandro: ‘You can be Cassandro, but leave that arrogance, that egotistic behaviour, leave all that drama to the side.’ I have to find the balance between the two.”

Cassandro/Saul now does a lot of motivational speaking, and says he is no longer wrestling for the money. “This is not a business for me. I’m the doctor’s business right now, because I’m paying thousands of dollars to fix my broken body.” Having just turned 44, he still envisages wrestling for another three to five years, and even after that he’ll continue to train aspiring luchadors, in Mexico, London and elsewhere. “It keeps me fresh, it keep me young,” he says. “If I would stop, if I wouldn’t train, I would become a bitter motherfucker.”