Nick Swinmurn, Zappos

After an unsuccessful hunt to find a pair of shoes the right size, Nick Swinmurn was inspired in 1999 to set up Zappos, an online shoe-retailing business.

By 2007 the company's revenues had grown to more than $800m.

The firm was acquired by Amazon in 2009. Nick Swinmurn's latest venture is Dethrone, which sells clothing online.

Key advice

You must force yourself to stay focused on your idea - don't let yourself get distracted, he says.

"The key is being scrappy. It's the guys that they see an idea and they don't know how they're going do it but they're going to try everything and just fight and claw and keep adapting, keep trying things."