At the start of the month, Cristiano Ronaldo broke yet another record within the footballing world. 

The Al-Nassr superstar was, as per finance experts Bloomberg, declared the first ever billionaire player, with an estimated £1.04billion fortune accrued from his earnings on the pitch, lucrative endorsement deals, property empire, and investments. 

But to one retired player, Ronaldo's staggering wealth is mere chicken feed. 

There was no way for Arsenal star Mathieu Flamini to accrue his billions during his playing career, which took place over the 2000s and 2010s when salaries - although unimaginable to most - were some way off the megabucks up for grabs in the 2020s. 

Nor did the former AC Milan and Crystal Palace midfielder garner particular attention as one of the media standouts playing for France, earning just three caps during his international career. 

But Flamini's 2019 post-playing career move into biochemicals has paid serious dividends, with the CEO now in possession of a net worth of an estimated £10bn, as per the Sun. 

In 2008, while still at the top of his game, he co-founded GFBiochemicals, a company focused on creating sustainable alternatives to fossil-based products. 

Now, years after quietly launching the venture, Flamini is a leading voice in climate innovation and environmental responsibility, and one of the wealthiest athletes on the planet.

Such is Flamini's influence in the industry that he has been invited to speak at Harvard Business School, and the EU Commission. 

This week Flamini even met fellow eco-warrior King Charles III after becoming a member of the Circular Bioeconomy Alliance. 

As Flamini shared on Instagram, this is 'where global leaders and Indigenous voices are shaping the future of the bioeconomy.'

GFBiochemicals' green credentials have been burnished by their invention of groundbreaking production of levulinic acid, which reduces CO2 formed when manufacturing products like detergents by up to 80 per cent. 

Flamini has also co-founded a supplement range called UNITY alongside former Arsenal team-mate Mesut Ozil, which was developed with scientists from the University of Westminster. 

The 41-year-old has previously shared that he was inspired after growing up as a fan of both 'football and sustainability'. 

'I grew up in Marseille near the sea, and was aware of the environmental questions around ocean plastics and chemical pollution from a very young age,' he shared. 

'We didn't know if it'd be energy, chemical or urban recycling, and we just ended up meeting with a team of scientists in Milan and started moving in that direction.'

A lifelong advocate for healthy living, Flamini has also followed a plant-based diet since he was 15 and believes that lifestyle helped extend his career. 

He is also pushing for more sustainability in football, from how shirts are produced to how fans travel to games.

'Climate change and sustainability is a hot topic these days,' he told the Times earlier this year. 'But we need to understand we are not only thinking about saving the Amazon rainforest. We're actually thinking about health.

'Take the Premier League. They have a business model to fulfil for the next 30 years and pollution is becoming a problem. In more parts of the world, kids aren't practising outdoors because of high pollution.

'If you have fewer people practising, fewer are following the sport, and the talent base declines. That's relevant.'

Rather than demanding sweeping change, Flamini believes football's global reach can drive impact through small, practical steps, including using solar power, recycling materials, offering plant-based food and encouraging fans to travel more sustainably.

But not all of Flamini's messages have gone down well with supporters on social media. 

The former player has found himself the subject of light teasing on X (formerly Twitter) for his sincere messages of self-improvement, with some mockingly comparing him to Jake Humphrey, host of the High Performance podcast. 

'People do "detox days" on weekends, then eat junk all week,' Flamini captioned a picture of himself drizzling chilli oil on half a pizza. 'Try to do the opposite. Eat clean 5-6 days, allow yourself 1-2 cheat days.' 

One commenter joked: 'Jake Humphrey just fell to his knees in Waitrose reading this'. 

Another of Flamini's posts offered the somewhat basic advice: '~80% of your brain, heart, and muscles are made of water. 

'So if you want to be at your BEST, you *must* drink water. It is not negotiable. Your body NEEDS this precious liquid to function properly. I try to drink up to 3L every day.' 

Due to his success to his success in business however, for all of those making light-hearted jokes about Flamini's advice, there are many, many more minded to follow him.