Abstract: Want the definition of a true leader? I have faced many.

I have often been asked who were my favourite interviewees - those I remember the most fondly. I can do one better than that and talk about the one person I have interviewed who stands head and shoulders above the rest.

In the 20 odd years I have been in commercial breakfast radio I have been lucky, and often unlucky, enough to sit opposite hundreds of 'leaders'. I use the word leaders in inverted commas because they share the term only in that listeners looked up to them in some manner of form and for some reason or other, and thought them deserving of some measure of adulation.

They were a motley assortment of politicians, musicians, actors, writers, sportsmen and women, adventurers, socialites, and, my personal nemesis - 'celebrities'. I use the word celebrities in inverted commas because it's someone else's definition, not mine.

Some were given valuable airtime because I considered them worthy, and because I thought they had something valuable to say. Many, however, were thrust in front of me because they were promoting their latest concert, book, DVD, or just themselves in general, and their manager had managed to convince my programme manager of the value of their presence on my show. A lot of management discussion, but very little direction.

As a result I have become inured to the appeal of the power, and I have developed a keen sense of what is chaff and what is wheat in terms of true leadership. I have listened, observed, been amazed and inspired, disappointed and sickened; and developed the capacity to quickly uncoil the spin and strip away the layers of paint that have been used to cover the cracks of a person's popular image.

In terms of having the characteristics of a true leader, unfortunately most have failed dismally. One or two have shown promise, and, with a little hard work could one day make the grade. But if you were to ask me whether any of them stand out as being of inspirational character, strength, integrity, compassion and humility, I'd say "yes - only one".

I know what you're thinking, so let me make something clear straight away: it's not Nelson Mandela. That would be too obvious. Besides, I have never met him. However, there are intriguing links and comparisons between the two.

They were both attacked and imprisoned during apartheid, but whereas Mandela will obviously never forget his incarceration, this person will wake each day with a stark reminder of the price he paid in his fight for human rights.

They both studied law and were politically active, and committed themselves to defending the victims of apartheid, but whereas Mandela eventually left law, attracted by the power of politics, this person used the power of the law to effect real change.

While I'm at it: they've both published books - and even both received the coveted Alan Paton Award for their written works, one of them twice - and, speaking of awards, they have both deservedly received a host of honourary doctorates from some of the world's leading universities.

On top of all this they have both worked their way to the very top of their respective fields and so both deserve the title of 'leader'. Streets have their names - even though they're both still alive - and after busy lives serving others, they have both retired, although their services are still in demand, and can at long last enjoy their twilight years with their families.

But there is one important difference: whereas Nelson Mandela has been catapulted into superstardom and everyone recognizes his image, the same can't be said of the other - Albie Sachs.

That is why, for me, he remains head and shoulders above everyone else.

He was one of those interviewees I really wanted to talk to, not because of who he was - a leading Constitutional Court judge - but because of what he was. He was the embodiment of leadership: honourable and deeply principled, softly spoken but firm in his resolve, and sincerely concerned for the welfare of others.

As he sat before me and answered my questions with an impish smile and a genuine interest, he showed himself to be a man of deep intellect and a continually enquiring mind. He also displayed continued evidence of his inexhaustible quest to find the correct balance for the rights of all South Africans; all the time brutally aware that such a balance could never be attained without a degree of tension and emotional conflict, and that people always got hurt.

But more importantly he left me with the indelible impression that this upset him, and that because human emotions were involved his decisions were never easy, but they had to be made. He also had every reason in the world to be bitter, but chose instead to embrace the task he had been given with humility and passion. For that reason he will always remain a true leader in my mind, and my favourite interviewee.

Originally published in the February edition of Leadership magazine, http://www.darylilbury.com