Mr Lee Kuan Yew was a worrier. But he was a problem solver too - not just of problems today, he anticipated problems to come.

That's why the Housing Board, and the rest of Singapore under his leadership, was continuously looking at problems and solutions, and continuously sharpening our skills.

When it comes to solving problems, Singapore is extremely disciplined. I would say this was a personal trait of Mr Lee's and it percolated rather effectively into the civil service. That's how a lot of his ideas got implemented.

While I was chief executive of HDB, he asked me periodically to take him on tours around the housing estates. He was not just a leader sitting in an air-conditioned room. He wanted to see things first-hand.

Around the early 1980s, we noticed that certain housing estates attracted people of some ethnic groups more than usual. Mr Lee was worried they would create ethnic enclaves.

Out of this, HDB introduced the ethnic quota system. This came out of having a leader who was circumspect and always examined what was happening on the ground.

I had quite a few one-to-one lunches with him in the Istana, where he would ask me very pointed questions. Through our interactions, I learnt that he was a ruthlessly rational person.

You could disagree with him to his face provided you could explain to him with good reason why, and he would agree with you if it was reasonable. This was a side to him that probably not many Singaporeans have understood well.

He did not worry about his face, he worried about Singapore.

He was a master persuader. He persuaded people and accepted people persuading him, but nothing arbitrary was acceptable or tolerated, and his reputation of toughness came from the fact that he did not tolerate anything that was not rational.

I will remember him most for enabling Singapore to move from Third World to First. Between 1960 and 1985, we turned a backward city into a place where there are no homeless, no squatters.

Today we have no poverty ghettos. Through HDB, we integrated and upgraded the poor into HDB estates with no ethnic enclaves. How many cities in the world can boast this?

It did not happen by chance, it happened by spotting and solving these problems, by anticipating instead of reacting.

When he first became prime minister, he introduced a lot of policies which were against world trends. One was to build high-rise, high-density housing. They were condemned in those days by experts in the developed world.

For many years, I was fascinated by his daredevil approach and wondered what gave him the courage to go ahead.

Then it dawned on me: When you have thought through a problem very carefully, you don't give a damn what people say. Then you have the courage to go ahead to do it.

And this, to me, was his core value: clarity equals courage. It had a profound influence on my approach to work.

He created modern Singapore and nurtured modern Singaporeans. Our discipline and strong sense of nation - we all owe these to him.