It seems clear that Nelson Mandela is an amazing man. It also seems that everyone that he met succumbed to his charm and manner. We frequently hear about some people having 'presence'. From the portrayals in the book and the movie, Mandela had bucketloads of presence. He was naturally charismatic; he smiled a lot (there's a mini lesson in that for me!); and he took an interest in whoever he was talking to. He engaged them - even when they were hostile.
What follows is assumption on my part, so you can judge the validity of it. I think that Mandela was/is very conscious of the impact that he has on the people he meets. He knows that he can charm the birds from the trees, and he uses this to his advantage. I suspect that he also had to work hard to develop his natural ability into a skill that he could deploy to great effect.
In other words, he identified a key strength and carefully crafted it over many years.
So the question for us - do we know what our strengths are and are we actively honing them to maximise their impact?