SINGAPORE - Judge of Appeal Chao Hick Tin, the only judge to have served under all four post-independence Chief Justices, will retire on Thursday (Sept 28) on his 75th birthday, after more than 50 years in public service in key positions.

On Wednesday, a rare valedictory reference - last held in 1990 for the retiring Chief Justice Wee Chong Jin - was conducted to honour Justice Chao and his contributions to Singapore.

It was attended by Deputy Prime Minister Teo Chee Hean and Law Minister K. Shanmugam, as well as fellow judges and lawyers.

Chief Justice Sundaresh Menon, Mr Shanmugam, Professor S. Jayakumar, Attorney-General Lucien Wong, Law Society president Gregory Vijayendran, Supreme Court registrar Vincent Hoong, and Judge of Appeal Andrew Phang gave speeches to pay tribute to Justice Chao.

Mr Shanmugam revealed how Justice Chao, as a 25-year-old officer in the Attorney-General's Chambers, had played a pivotal role in securing Singapore's long-term water security when he represented the country at a United Nations event in 1968, following its separation from Malaysia in 1965.

During the discussions at the UN Conference on the Law of Treaties, a Malaysian representative acknowledged that "some treaties might be so fundamental to the very existence of States that they simply could not be dispensed with, whatever political differences might arise", said Mr Shanmugam.

"For example, the new island State of Singapore was dependent on Malaysia for its water supply; The treaty under which Malaysia had to supply a certain quantity of water daily to Singapore could not be terminated or suspended between the two States for any political reason," the Malaysian representative was quoted as saying.

Mr Shanmugam said Justice Chao heard the remarks and had the presence of mind and astuteness to act, having realised quickly how important the statement was because water from Malaysia was linked to Singapore's very survival.

He said Justice Chao reiterated "that the representative of Malaysia had said that even the severance of diplomatic relations, which he hoped would never occur, would not affect the water agreement between Singapore and Malaysia."

In doing so, Justice Chao had put on official record Malaysia's express confirmation that our water agreements cannot be terminated, whatever political differences might arise, said Mr Shanmugam.

"Lawyers will understand the importance of the Malaysian acknowledgment. And the importance of having that acknowledgment, as a matter of UN Record," said Mr Shanmugam, adding how the acknowledgment has given Singapore added confidence whenever Malaysia has tried to take issue with the water agreements.

"We owe Justice Chao a deep debt of gratitude."

Other speakers at the event also lauded Justice Chao for his well-known attributes in the legal fraternity, such as his humanity, patience and kindness, as well as his wisdom, clarity of thought and the courage to do what he believed was right.

CJ Menon said he tried his first large case before Justice Chao nearly 30 years ago, describing it as "wonderful experience to have the privilege of doing so before a Judge who was patient, attentive, completely in command of his papers, and yet so willing to listen to what counsel had to say".

"It was the extraordinary humility of Justice Chao that left a deep impression on me as a young lawyer," he added.

Justice Chao obtained his bachelor's degree in law from University College, London in 1965, and his master's degree a year later.

He began his legal career in 1967 in the Attorney-General's Chambers, where he was a key member of the team that negotiated the UN Convention on the Law of the Sea.

He was appointed judicial commissioner in 1987 and elevated to a High Court Judge three years later. He was appointed a Judge of Appeal in 1999.