(CNN) When Formula E chief Alejandro Agag announced in 2012 that he would be launching a new all-electric racing series, few could have predicted just how rapidly the circuit would grow.

Formula One supremo Bernie Ecclestone was the loudest of many critics who predicted the idea would quickly fizzle out, says Agag.

But the premier electric series is set for its 50th race in its fifth season in Hong Kong this weekend.

"Race number 50 is a very big moment for us," Agag told reporters in London. "I remember Bernie Ecclestone told me: 'You will never make your first race."

Ecclestone, who was Formula One chief executive for nearly 40 years, was just one of many people who have been forced to eat their words.

"I have Bernie on, you know, probably the highest consideration as everything, as a friend, as a businessman, as a creator of Formula One," Agag said.

"One week before my first race. He told me: 'I'm glad you were right and I was wrong.'"

'Cherry on the cake'

Considered one of the world's fastest growing sports, Formula E attracted more than 300 million viewers globally to watch at least one race on TV last season, according to Forbes.

An average of 27.1 million watched each individual race, a huge increase on the 18.6 million that tuned in for each race during the 2016-17 season.

Formula E's rapidly increasing popularity convinced the BBC, the UK's national broadcaster, to purchase live rights for the current season and this weekend's Hong Kong E-Prix will be the first race broadcast on a free-to-air channel.

"It is kind of the cherry on the cake to be on BBC," Agag says. "It shows that the championship is on its highest moment so far. We are in the best moment and Porsche and Mercedes are still to come, they're coming next year.

"Every time we see more public going to the races, there is more and more following on TV and on social media and digital and on top of it we start to make some breakthroughs with some really big free-to-air channels."

Agag admits he has "no idea" how many people will tune in to watch the Hong Kong E-Prix, but says he would be delighted with 400,000 live viewership.

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Despite his sport going on free-to-air TV and the exposure this provides for a potential new fan base, Agag believes Formula E's strength lies elsewhere.

After a conversation with the CEO of one of the world's biggest telecom companies, the 48-year-old said the priority of organizations is digital audience growth.

"He was completely focusing only on that," Agag says. "The TV audience maybe grows 10%, 20% -- 40% in our case -- year on year, but the digital grows 500%.

"When I was in Mexico, my kids were away and two of my kids didn't watch the Mexico race so I said to the kids: 'How are we going to watch the Mexico race, we haven't recorded it on Sky or whatever?'

"My kids look at me like I'm an idiot ... and my kid takes his phone, goes on YouTube, goes on airplay and there is the race on TV.

"Things are shifting and people are watching more highlights than live races and you do have to adapt to that -- and the kids, you know, the new generation gets that."

'Changing in our direction'

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Formula E's growth during its five years of existence has been reflected in the changing outlook of society.

Companies and individuals have become more eco-conscious, looking for ways to go green and reduce their carbon footprint, and the transition from petrol and diesel to electric cars has been at the forefront of this change.

"In 2012, there were 190,000 electric cars on the road around the world," Agag says. "The forecast, more or less, is that we're going to end up very close to or maybe a little bit above eight million.

"So we're going from 190,000 to eight million -- of course eight million is very small compared to a billion cars or vehicles in general out there. But from 190,000 to eight million is a huge growth.

"If you look at all the car brands modifying their production lines to adapt to electric and putting electric motors, if you look at the Paris Climate Agreement, if you look at the rules in European Union about CO2 emissions, the world is changing and the world is changing in our direction.

"It's not changing in any other direction, it's changing in our direction."