How the chocolate bar became a million dollar idea

Nowadays, the world spends close to $100bn a year on chocolate bars, making them one of the most popular snacks in history.

But for centuries, chocolate had only been a drink. No one knew a way of making it into a solid food. That is until a 19th Century Englishman - Joseph Fry - worked out how to do it.

Aaron Heslehurst now explains.

Video producer: Jeremy Howell