The Idea: In 2009, Will Dean was a British Army bomb disposal officer with an idea he couldn't shake - a brutal outdoor obstacle race designed to test mental toughness as much as physical fitness. He pitched it to Harvard Business School professors. They told him nobody would pay to crawl through mud and jump over fire. Dean ignored them, enrolled in the MBA programme anyway, and used the course as cover to build his business plan. He scraped together $7,000 in personal savings, secured a venue in Pennsylvania, and put up a basic website. He offered early-bird tickets at $75 each. Within three weeks, 5,000 people had signed up. Zero marketing budget. Zero outside investors. Just a guy who believed people were desperate for something harder than a 5K. This was the beginning of Tough Mudder.

The Execution:

• May 2010: The first Tough Mudder event sells 5,000 tickets in 3 weeks - entirely through word of mouth and early-bird presales. Dean proves the concept with no outside capital.
• 2011: Tough Mudder expands to 20 events across the US and UK, capitalising on the growing obstacle race craze. The waiting list grows faster than new events can be added.
• 2012: The company hits $10M in profit and begins expanding globally - without ever taking a dollar of outside investment.
• 2014: Tough Mudder reaches 2 million lifetime participants across 10 countries. The brand has become a cultural phenomenon, with participants wearing orange headbands as a badge of honour.
• 2016: Annual revenue crosses $100M. Dean quietly cashes out a portion of his stake for "millions" while remaining at the helm. Three million people have now completed a Tough Mudder event.
• 2019: Tough Mudder files for involuntary Chapter 11 bankruptcy with $7-10M in unpaid vendor debts and mounting co-founder litigation. Dean is forced to resign as part of the restructuring.
• February 2020: Spartan Race acquires Tough Mudder's assets for $700K in bankruptcy court - a brutal ending to a $100M+ business.
• 2024: Dean's next venture, Immersive Gamebox, has raised $65M, opened 40+ locations globally, and welcomed over 1 million players - backed by Netflix and others.

The lesson? Dean built a $100M business from $7K by solving a problem people didn't know they had - the desire to suffer alongside strangers. He ignored every expert who told him it wouldn't work, presold his way to proof before spending a cent, and created a community around shared struggle that made marketing almost unnecessary. The ending was messy. But the arc from $7K to $100M, entirely bootstrapped, on the back of a single insight about human psychology, is one of the great startup stories of the last decade.