Original: On 18 July 2007 in Johannesburg, South Africa, Nelson Mandela, Graça Machel, and Desmond Tutu convened a group of world leaders to contribute their wisdom, independent leadership and integrity together to the world.
Simplified: On July 18 2007 in Johannesburg, South Africa, Nelson Mandela, Graça Machel, and Desmond Tutu began a group of world leaders to help the world.