The mark of a great leader is being prepared to tell your people what they don't want to hear.
It's being ready to stand up for what you believe is right, even when this entails overruling cautious advisers, or ignoring discouraging opinion polls.
A great leader knows that vindication may not come immediately, that received wisdom can move slowly (sometimes too slowly, in a democracy, to secure re-election).
But in the long run, we can see who stands on the right side of history, and who does not.
Nelson Mandela and FW de Klerk, each former South African presidents, fit into the former category.
Both men have flawed records, (yes, even Mandela) but at a crucial time they had the courage and wisdom to steer South Africa away from the abyss.
They dismayed hardliner supporters with their willingness, firstly, to talk to the other side, and secondly, to then make painful compromises.
They took risks that could have destroyed their careers, but the quality of their leadership was a crucial ingredient in what we now see as the near miraculous peaceful end of Apartheid.
I can think of other examples of bold, principled leaders the reforming Mikhail Gorbachev of the mid-1980s, and some of the Protestant and Catholic politicians in Northern Ireland who helped bring the peace process to fruition.
So what has this got to do with our world today?
This week, Hillary Clinton, the US secretary of state, will be  trying to encourage progress in talks between ethnic Greek and Turkish leaders on the island of Cyprus.
Expectations on Cyprus are low.
Rarely has the prospect of reunification of that troubled island looked more remote.
On the list of apparently insoluble political problems, Cyprus rates high. Almost as high, in fact, as the mother of all of those insoluble problems, the Israeli-Palestinian conflict.
Well, it just so happens that Clinton will also be wading into that one in the next few weeks.
Again, it seems that only eternal optimists, or the hopelessly naïve, believe that anything will come of the new round of talks between the Israeli and Palestinian leadership.
At this point, I cast back my mind to my childhood.
I grew up in the 1970s and 1980s, in Africa and Britain. Then, it was difficult to imagine that the end of Apartheid would not be accompanied by a bloodbath, or that Irish Catholics and Protestants could reach a lasting political settlement.
I know that it is simplistic to lump together such diverse places as South Africa, Northern Ireland, Cyprus and the Middle East.
Of course, each has its own complex history, and every community has its unique list of grievances and injustices suffered.
But if there is to be any progress in talks on the Middle East or Cyprus in the next few weeks, it can only come through courage and a willingness to compromise on the part of those leaders involved.
What is frustrating is that in both places, we have a pretty good idea of what a final settlement would look like.
It's the getting there that is so difficult.
So, Cyprus, Israel and Palestine where are your Mandelas, your FW de Klerks, your Sisulus and Tambos? Where are your John Humes?
Do you have leaders who will tell their people to give up on cherished but impossible dreams, and work for peace here and now?