Prime Minister Lee Hsien Loong first met Emeritus Senior Minister Goh Chok Tong in 1978, and something Mr Goh said then has stayed with Mr Lee all these years.

At the launch of Mr Goh's biography, Tall Order: The Goh Chok Tong Story, Mr Lee recounted how Mr Goh was then a new MP, having been first elected two years earlier.

"I knew he had built a strong reputation, having turned (shipping line) NOL around," he said.

"A snippet of our dinner conversation has stayed with me all these years. Chok Tong recounted how in Parliament he made it a point not to make speeches about shipping, but instead to talk about other issues."

Mr Lee shared this yesterday as he outlined the "productive and harmonious" 40-year relationship he has had with ESM Goh.

"I am sure neither of us expected that we would go on to have such a long engagement, spanning more than half our lives," he said.

He recalled too how, when he was a student at Fort Leavenworth in the United States, and was required to make a presentation on Singapore, his mother had asked Mr Goh whether he had pictures which Mr Lee could use. "Chok Tong kindly sent some slides of a kite-flying competition in Marine Parade, then a new housing estate with lots of empty spaces," said PM Lee.

They became closer when Mr Goh took over as defence minister in 1982 and Mr Lee was in the General Staff of the armed forces.

Mr Goh "did not have a background in defence matters, but he brought a clear and open mind to bear on the issues", Mr Lee recalled.

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"He listened to arguments put up by the professionals, and asked the right questions. When he was satisfied that we knew what we were doing, he trusted and empowered us, allowing young officers who proved themselves to make major decisions and break new ground."

It was while Mr Lee was working under Mr Goh at the Ministry of Defence that Mr Goh asked the future PM to join politics. Mr Lee agreed, and the pair became colleagues in Cabinet. When Mr Goh succeeded Mr Lee Kuan Yew as prime minister in 1990, Mr Lee became his deputy.

And when Mr Lee took over as PM in 2004, he asked Mr Goh to stay on as senior minister.

"Chok Tong began as my mentor; we became comrades; we remain lifelong friends. We have somewhat different temperaments and instincts, but we complemented each other well," he added.

"We developed a strong partnership, not just between the two of us, but also across the team."

As a leader, Mr Goh does not make up his mind in a hurry. But having made a decision he is firm and steady, so his ministers know where they stand and what they are trying to achieve, Mr Lee said.

"I think I have given enough preview to whet your interest in Volume 2 of Chok Tong's book, when it comes out," he quipped.

The first volume launched yesterday covers the significant episodes in Mr Goh's life, from his childhood years to his career in the civil service and private sector, his entry into politics and his eventual succession as prime minister.

"Through this volume, Singaporeans, especially the younger ones, will discover the human being behind Chok Tong's public persona," Mr Lee said.