Image copyright Jaime Ruiz Image caption If customers can eat Super Astro's signature sandwich in less than 20 minutes they get it for free

As a proud Mexican wrestler Super Astro won't take off his mask or reveal his real name.

Now 58 years old, while he still competes in the ring from time to time, his main job is running his sandwich shop in Mexico City. Which he does while still wearing his silver and black mask.

The eatery - Tortas Super Astro - is a homage to Mexican wrestling, known in its homeland as lucha libre (free wrestling).

Pictures and paintings of Super Astro and other masked heroes line the walls, and it specialises in giant portions to meet the calorie needs of the numerous wrestlers among its regular customers.

Image copyright Jaime Ruiz Image caption Masks continue to be an integral part of Lucha libre

The signature sandwich is a torpedo-shaped roll called the Super Special Astro.

Some 16 inches (41cm) in length, it weighs 2.5kg (5.5lb), and it is filled with beef, chicken, ham, bacon, sausage, cheese, omelette, onions, tomatoes and avocados.

It costs 270 pesos ($17; £12), but if you can eat it in less than 20 minutes, you don't have to pay. Not many people manage that feat.

Super Astro first opened the business back in 1986 because despite the enduring popularity of lucha libre in Mexico, the wrestlers were paid very little.

He says he realised that there would be demand for a sandwich shop that provided giant amounts of food for low prices. And at the same time, that the eatery would also give him a more dependable source of income.

Fast forward 26 years, and Mexican wrestlers still don't get paid very much, particularly in comparison with the stars of the US behemoth that is World Wrestling Entertainment (WWE).

For while WWE wrestlers can easily pocket $2m (£1.3m) a year, the best lucha libre fighters earn about $1,600 at the largest weekly events, and most are paid significantly less.

Lucha libre facts

Image copyright Daniel Berehulak

Is it a sport? Like most modern forms of wrestling, lucha libre is known as "sports entertainment". This is because the matches are designed primarily for spectacle and entertainment rather than as an out-and-out competitive sport

Why the masks? Most lucha libre wrestlers wear masks due to a tradition that dates back to the 1930s

Lucha libre wrestlers are not allowed to pull off an opponent's mask. Masks are generally only removed if a player loses

As well as wearing a mask, the wrestler take on a stage name, with some playing hero characters, and others performing as baddies

The wresters are known as "luchadores", and traditionally they perform more aerial moves than wrestlers in the US-based World Wrestling Entertainment

Despite continuing grumbles from the Mexican wrestlers that the promoters take too much of the cash, there is simply not a great deal of money in the industry.

Although lucha libre has a loyal fanbase, its popularity in Mexico is dwarfed by the likes of football, baseball and boxing.

And while the biggest two or three lucha libre events of the year can attract crowds of 17,000, most weekly fights see attendances of between 1,000 and 3,000 people, with tickets costing about 300 pesos.

Image copyright Getty Images Image caption Lucha libra masks come in a kaleidoscope of colours

Numerous fights are shown on TV, but one of the two biggest lucha libre organisations, the family-owned Lucha Libre AAA, continues to make most of its money from ticket sales, and sponsorship.

As a result, AAA's annual turnover is about $20m, compared with $500m at WWE.

The lucha libre industry also has to cope with Mexicans being able to watch WWE fights on their televisions, and even with WWE holding a few meetings in Mexico each year.

Yet despite the pressures on lucha libre, the small firms that form its backbone - such as the makers of the celebrated masks, and AAA itself - continue to have big ambitions to thrive.

'Cyclone McKey'

Lucha libre traces its origin back to the second half of the 19th century. It takes its name from the fact that many more wrestling moves were allowed than the more formal Greco-Roman wrestling from which it developed. Lucha libre became popular across the whole of Mexico in the 1930s.

The wearing of masks started around the same time when an Irish wrestler living in Mexico known as "Cyclone McKey" wanted to become the first masked wrestler.

Image copyright Jaime Ruiz Image caption Victor Martinez says he isn't concerned by Chinese-made masks

Cyclone McKey got a mask made for him out of goat skin by a shoemaker called Antonio Martinez.

Despite not liking the first design, the Irish fighter started to order additional batches from the shoemaker, and soon other wrestlers were copying him, and going to Mr Martinez for their own masks.

The business is today called Martinez Sports, and run by the late Mr Martinez's son Victor.

One of a handful of traditional wrestling mask makers in Mexico, it produces 450 per week, from bespoke designs that require 17 measurements of the wrestler's face, and cost $100, to more affordable off-the-peg versions. These days the masks are made from man-made fibres to make them lighter and more breathable.

Despite much cheaper Chinese-made masks being available, both worldwide and in Mexico itself, Martinez Sports continues to enjoy strong business.

It supplies a majority of the 250 or so professional wrestlers in Mexico, and in recent years has set up a website to sell to wrestling fans around the world.

Victor Martinez says: "My dad was a perfectionist, and he left me that legacy. It is my responsibility to maintain his prestige.

"Today the masks remain one of the key elements that give life to wrestling.

"The Chinese imitations look amateurish, they never have the quality of a professional mask, the quality isn't the same."

'Supporting dreams'

At AAA, the organisation is working hard to create new revenue streams for the sport, such as recently helping to create a wrestling video game.

It also hopes to get lucha libre onto television screens in the US via establishing a reality TV programme looking at the lives of wrestlers.

Image copyright Jaime Ruiz Image caption Nicolas Sanchez, aka Modern Hercules, says wrestling 'is a part of Mexico'

Back at Super Astro's sandwich bar, Super Astro says despite the pressures it is under, lucha libre will continue to be popular.

"There is still a lot to offer to the public that is faithful to us," he says. "The public still demanding it, enjoy it and pay to see a good show."

His optimism is echoed by former fighter Nicolas Sanchez, 52, (known to his old fans as Modern Hercules), who now runs a gym in Mexico city where wrestlers train.

"Wrestling is part of Mexico, lives in the heart of people," he says. "Here come young people with enthusiasm, they want to be wrestlers, who dream and step into the ring to be stars. We and the coaches are here to support their dreams."

However, Victor Martinez is not so optimistic, grumbling that lucha libra is losing some of the more intricate and acrobatic wrestling moves of the past, to instead become more like the showbiz and brute force of WWE.

"Wrestling is not what it was before," he says. "Now it's more spectacle, more circus and less sport. But people still like it, that will not change."