(CNN) -- Veronica Campbell-Brown knows a thing or two about upsetting the odds. 

The 29-year-old Jamaican sprinter has had to overcome grinding poverty to become one of the greatest Olympians her country has ever produced. 

After being spotted running barefoot at a school sports day, Campbell-Brown burst on to the track and field scene when she won silver as part of Jamaica's 4x100 meters sprint team at the 2000 Sydney Olympics. 

That was just the start. 

She went on to win gold in the 200 meters at both the 2004 Athens and 2008 Beijing Olympics. Now she faces her toughest test at her fourth Games. 

CNN Photos: On the fringe of an Olympic dream 

If she emerges triumphant at London's Olympic Stadium in August, she will be the first person in history to win three consecutive gold medals in the distance. She is in good form too. Last year she ran the 100 meters in 10.76 seconds, the second quickest time in history. 

CNN's Human to Hero caught up with the Trelawny-born sprinter -- who hails from the same Jamaican parish that has given the world champion men's sprinter Usain Bolt -- to talk about London 2012, her rivals and why a third gold would be the icing on the cake. 

Growing up in poverty 

"I have five brothers, four sisters, so you can just imagine the competition in the house. It helped me be very competitive, strong and independent," Campbell-Brown said. 

"I used to race the boys and win. So I knew I had a special gift and should work on improving it. 
Did she come from a small family?
"I have five brothers, four sisters,