A BBC series is asking some of the world's most influential people about the defining moments in their life.
As the Archbishop of Cape Town, Desmond Tutu was one of the key leaders in the fight to rid South Africa of apartheid. More recently he chaired the country's Truth and Reconciliation Commission, which sought to heal the scars of apartheid.
Tutu is a Nobel peace laureate
The biggest defining moment in my life was when I saw Trevor Huddleston and I was maybe nine or so.
I didn't know it was Trevor Huddleston, but I saw this tall, white priest in a black cassock doff his hat to my mother who was a domestic worker.
I didn't know then that it would have affected me so much, but it was something that was really - it blew your mind that a white man would doff his hat.
And subsequently I discovered, of course, that this was quite consistent with his theology that every person is of significance, of infinite value, because they are created in the image of God.
And the passion with which he opposed apartheid and any other injustice is something that I sought then to emulate.
Defining Moments will run until 23 July on BBC World Service's World Today programme. You can also read people's recollections on BBC News Online.