Former Cabinet minister S. Jayakumar stepped down from politics in 2011, but carries on doing public service. He is still a regular face at the Ministry of Foreign Affairs (MFA) where he is a senior legal adviser to Minister Vivian Balakrishnan.

Whenever Singapore is involved in complex legal or diplomatic issues, Professor Jayakumar is called upon to help, given his institutional knowledge and experience.

For his "sustained and invaluable contributions to the nation", he has been conferred the Order of Temasek (With High Distinction), topping the list of this year's National Day Award recipients. He is the 10th Singaporean to receive the nation's highest civilian honour.

The 80-year-old, who served as diplomat and minister, said he was grateful and surprised by the gesture: "All these matters I have been involved with concern important national interests of Singapore. If Prime Minister Lee Hsien Loong and Foreign Minister Vivian Balakrishnan feel that it will be beneficial for me to share my experience and knowledge, how can I say no?"

This sense of duty to Singapore has been his motivating force in a public service career spanning close to 50 years.

As a young law professor, he was called on to be Singapore's permanent representative to the United Nations from 1971 to 1974. He returned to academia and was dean of the National University of Singapore (NUS) law faculty till he joined politics in 1980.

As a law academic, he was also roped in on challenging issues like Pedra Branca and the water agreements with Malaysia. So it was no surprise that he would be the go-to person when Singapore got involved in complex legal issues.

But what Prof Jayakumar brought to the table was not just legal expertise, but also diplomatic nous, say those who have worked with him.

As foreign minister from 1994 to 2004, he oversaw a range of complex bilateral issues, including an agreement under which the Malayan Railway would vacate the land at Tanjong Pagar, the Pedra Branca disputes with Malaysia, as well as transboundary haze problems involving Indonesia.

Even as he fought fiercely to protect Singapore's legal interests, he never forgot the importance of maintaining good relations with neighbouring and other countries.

Singapore's successful election to a non-permanent seat at the United Nations Security Council from 2001 to 2002 was "a reflection of his strong leadership and influence in fostering extensive ties and Singapore's esteemed global reputation" said an MFA spokesman.

In 2007, Prof Jayakumar led the team that successfully pleaded Singapore's case on Pedra Branca at the International Court of Justice at the Hague. In 2017, he was once again called upon to help when Malaysia filed applications to revise and interpret the judgment that awarded sovereignty over the outcrop to Singapore. Malaysia dropped its applications in 2018.

On why he continues to help, Prof Jayakumar, who had also held the Law and Home Affairs portfolios, said he hoped to contribute his institutional knowledge, and through doing so develop new generations of office-holders, diplomats and international lawyers. He had served as deputy prime minister, coordinating minister for national security and senior minister before stepping down from politics in 2011.

Working with the younger generation of public servants has been a great experience, he said: "They are very bright and hard-working. I also have learnt from them.

"Singapore now has an excellent new generation of diplomats and international lawyers. They can hold their own with any of their counterparts from other countries."

The MFA spokesman said his rich experience and strategic perspectives in managing sensitive bilateral and multilateral issues have benefited many of the younger generation of foreign and legal service officers working with him.

Said Ms Daphne Hong, director-general of the International Affairs Division at the Attorney-General's Chambers, who worked on the Pedra Branca issue in 2017: "It became apparent that he puts his entire mind, his entire soul, into what is in Singapore's interest. I get the sense that he thinks about how we can advance Singapore's cause all the time. It's constant and consistent."

This year, two Distinguished Service Order awards were conferred on Mr Koh Choon Hui, 79, chairman of the Singapore Children's Society (SCS), and Professor Wang Gungwu, 89, founding chairman of the Lee Kuan Yew School of Public Policy at NUS, and the former chairman of the ISEAS - Yusof Ishak Institute and East Asian Institute (EAI).

Mr Koh, a stalwart of the social service sector for over four decades, had not only expanded the SCS' reach but also nurtured many social service agencies.

One of his enduring contributions was to align the pay scales of social service sector workers with those of the civil service when he was acting honorary general secretary and vice-president of the National Council of Social Service from 1992 to 2000, laying the groundwork for the sector to recruit and retain staff. Said the Ministry of Social and Family Development: "His contributions have nationwide and long-term impact on the lives of many Singaporeans."

Mr Koh said of the award: "It is also a recognition of the many wonderful volunteers I have worked with over the decades who have given selflessly to help others. They have made my journey a very memorable and meaningful one."

Prof Wang, a historian who played a key role in building up and growing the three institutes, is recognised for strengthening Singapore's position as an independent base for leading research on China and East Asia among other things, said the Ministry of Education.

He said on Friday: "I have enjoyed all the work I have been able to do and learnt a great deal while doing it. This is an honour I share with my wife Margaret whose deep feelings for Singapore have made my work here all the more satisfying."

His wife, who died yesterday, had been a big factor in his decision to leave Hong Kong and return to Singapore in 1996 to lead the then Institute of East Asian Political Economy, which became the EAI.

A full list of this year's National Day Award recipients is available at the PMO website.