Plummeting 18,000ft on the end of a failing parachute is, admits former special forces operative Anthony “Staz” Stazicker, the worst possible time for a jacket zip to break.

“I was trying to deal with a chute malfunction with an undone jacket billowing around my face,” he recalls of the 2013 incident in the Middle East that saw him, against the odds, deploy a reserve canopy and escape unscathed.

“In the special forces we were used to better kit [than regular army personnel] but it struck me that it was odd to spend a lot of money on a jacket but not have a better-quality zip.”

It’s the kind of detail that the 40-year-old, whose 13-year-service included stints as a Royal Marine sniper instructor and demolition expert, can better control in his career 2.0 at the helm of outdoorwear business, ThruDark.

Co-founded with fellow special forces operative and Royal Marine, Louis Tinsley, in 2016, what began with an idea to improve the quality of military wear has evolved into a £13 million turnover outdoorwear brand selling mainly online to a market prioritising technical performance in clothing, whether mountain climbing or in the gym.

Headquartered in Poole, Dorset, he credits the near 90 per cent growth in turnover in the last three years to a“hardcore following” drawn to the pair’s elite military credentials. Notably, the popularity of Channel 4’s SAS: Who Dares Wins, which sees ex-army officials put lay recruits through the selection process, has brought both greater visibility to a force traditionally in the shadows — as well as the ThruDark brand itself.

“We went from a handful of followers on our social media channels to an extra 10,000 overnight after our clothing was worn on the programme,” says Stazicker who appeared on the show himself in 2021.

“There’s an authenticity to the brand; we’ve operated and thrived in some of the world’s most inhospitable places, the jungle, desert and heavy snow, so we know first-hand the best fabrics and technology needed in extreme environments.”

Indeed, having regularly customised his kit during military manoeuvres — for example, sewing on tent canvas to reinforce the elbows of jackets — it’s an approach that has informed the product range, with the use of the canvas-like nylon Cordura fabric long used in the armed forces to withstand rips and tears on harsh terrain.

What began with cold-weather expedition gear, bespoke mountain suits and arctic jackets to withstand minus 40 temperatures has expanded to skiwear and “athleisure” gymwear designed by the company founders and made in factories in Italy, Vietnam and Eastern Europe. For a customer base skewed towards 30 to 40-something professional males unfazed by price tags rising to £1,000 for a parka, it is evidence that the pandemic boom for outdoor adventurewear has been sustained as an increasingly higher-end and mainstream staple.

According to McKinsey’s 2024 State of Fashion report, revenues for the outdoor category in 2022 were 24 per cent higher than pre-pandemic era, a broader traction evidenced by the UK’s largest outdoor clothing and equipment retailer, Mountain Warehouse, which revealed record revenues of £386 million last year, the highest in its 27-year history.

ThruDark’s timing has chimed with the zeitgeist, though the path from the special forces to successful first-time clothing brand entrepreneur is not well trodden.

“We had a lot of scepticism from old colleagues because it was uncharted territory, but we always had this strong vision and were determined to make it work,” says Stazicker, who credits leaving the army on his own terms and a “career high” for smoothing the transition to civilian life.

“You get people at 42 or 44 years old after a 22-year army career with a pension that’s not enough for a good standard of living, so they have to work — but the military, which is very insular, is all you’ve known, so it’s hard to move on. Going into business with someone I knew and trusted really helped. Could I have done this on my own? Probably not.”

While lacking business experience, the pair, who are both “meticulous planners” and used to leading high-stakes operational missions, have deployed the same core traits of discipline, work ethic and quick decision-making. They liken learning the trade to rising through the military ranks, with a hands-on approach to everything from learning spreadsheets, packing the goods and visiting the factories.

However, coming from a world of “harsh feedback” and “zero tolerance for slacking off” has meant tempering the army’s more typically blunt communication style when dealing with his 40-strong team.

“There’s an emotional detachment often needed when operating in highly stressful environments, and I’ve had to learn to be much more empathetic to build rapport in the business environment,” he says, adding that he struggled initially with having too high expectations of the people around him.

“In the special forces everyone is emotionally invested and part of something bigger than them, but it can be harder in business to find people with the same passion for what you’re trying to achieve: you have to hold on to those that have it, because they’re like gold dust.”

Indeed, the old adage of being surrounded by the right people has been absolutely central to success. Having been introduced to the Poole-based Clark investment group in 2017, its founder Steven Clark came on board with the investment needed to propel the early product development and provide additional mentorship and incubation.

With a portfolio skewed towards opportunities rooted in founder experience, the firm has invested a significant proportion of the £5 million it has raised to date and believes ThruDark can be a £100 million concern within the next six years, primarily by capitalising on the nascent American market. Currently the brand’s fastest-growing market and one worth $10.5 billion in 2023, the focus will be on social media influencer marketing and tapping into Stazicker’s existing network of contacts, including US Navy Seals.

Despite the fast growth and optimistic trajectory, caution prevails regarding plans to expand into bricks and mortar, currently limited to a small presence in Selfridges department store in London and a unit on a business park at ThruDark’s Poole headquarters.

“It’s still a challenging climate on the high street. Business is stressful, particularly as you grow, because you’re very aware that more people are reliant on the company being a success, and cashflow is always an issue. But at the end of the day it’s just problem-solving — and we’ve always been able to make decisions,” says Stazicker.

ThruDark was the No 61 company on The Sunday Times 100 in 2024, our annual ranking of Britain’s fastest-growing private companies. To nominate your company for the 2025 programme visit thetimes.com/st100