How one woman become a billionaire from big pants

At 41, Sarah Blakely has just become the youngest self-made billionaire in the world. Not bad for someone who failed law school admission tests twice and went on to work as a meeter-and-greeter for Disney. Her next role as a door-to-door salesperson for an office equipment supplier in Florida saw her rise through the ranks to national sales manager.

Like all the best inventions, Blakely's epiphany came when she found she needed a product that didn't yet exist. A side line in stand-up comedy saw her stuck with what to wear for a show one night. Her white trousers allowed her normal underwear to be seen â€" the dreaded VPL (visible panty line).

Blakely had the brainwave of cutting the feet out of a pair of tights (or panty hose as they are known in the US) to create a smoothing and firming effect. However, when she wore the cut off tights underneath her trousers she found the tights rolled up her legs all night.

This wardrobe malfunction meant an idea was born. At 29, Blakely invested her life savings of $5,000 (£3,190) trying to come up with something flattering to wear under white trousers. Control hosiery Spanx was born and Blakely wrote the patent herself to save money. The name itself was on the saucy side while the slogan "we've got your butt covered" captured department store buyers' attention.

Blakely's sales background played a huge part in her success. In 2007 she told Bloomberg Business Week that everything about her journey to get Spanx off the ground entailed having to be a salespersonâ€"from going to the hosiery mills to get a prototype made to calling Saks Fifth Avenue and Neiman Marcus.

"I had to position myself to get five minutes in the door with buyers," she said. "My first account was Neiman Marcus. I cold-called them just like I had cold-called businesses when I was selling fax machines for seven years."

Neiman Marcus' hosiery buyer agreed to meet Blakely for just 10 minutes, during which she pitched her idea and took the buyer to the bathroom to do a "before and after" demonstration of the product.

Six months after setting up Spanx, in 2000, Blakely sent some samples to Oprah Winfrey's stylist and received a call from her production company saying the chat show host planned to include Spanx on her "Favourite Things Show".

Who needs advertising? Winfrey's recommendation saw Spanx go from a single product sold out of Blakely's Atlanta apartment to a billion-dollar business which has made its founder part of a tiny, elite club of women worth ten figures.

Further celebrity endorsements followed form singer Gwen Stefani and style icon Sarah Jessica Parker and Spanx got covered in women's magazines including Vogue as well as business magazines such as Forbes.

Spanx now generates almost $250million (£160million) in annual revenues with net profit margins of about 20%. And because Blakely has never received outside investment and the company remains hers and hers alone, stretchy pants have made her incredibly rich.

The company has been valued at $1billion (£638million) by four separate Wall Street investment banks. There are now 200 Spanx products sold in 11,500 department stores, boutiques and online shops in 40 countries.

As well as women's knickers, the Spanx brand now includes bras, legwear, swimwear and menswear. TV presenter Jonathan Ross admitted to wearing a Spanx control T-shirt to disguise a few extra pounds when he hosted the British Comedy Awards last year.

Blakely prides herself on finding her own way in business, and relying on gut instinct. She didn't have any business education and no board of advisers to give the benefit of their experience.

"Now I give speeches and I always ask: If no one showed you how to do your job, how would you be doing it?" she told Business Week. "Take a moment and ask that question. Often your way is better. Maybe it's a fresh new approach. If you are doing something the way that everyone is doing it, you are not really creating change by doing it that way."

Married to former rapper Jesse Itzler with whom she has a two-year-old son, Blakely now owns six houses. However, she's also pretty generous with her cash. To date she's donated about £17.5million to charities, with a focus on those who help girls and women.

In 2006, she launched the Sara Blakely Foundation to help women through education and entrepreneurial training. The Foundation's projects include Habitat for Humanity where the Foundation provided more than $150,000 (£96,000) in funding to build two homes for single mothers and their families through the Women Build Program in South Africa.

The program was created to encourage the involvement of women in the construction of Habitat homes. Spanx employees worked alongside students and the female homeowners for six weeks to build the houses.

Blakely has also funded scholarships for young women at CIDA (a higher education institution) in South Africa and donated $1million (£638,000) to Oprah Winfrey's Leadership Academy.