When Workers' Party (WP) MP Pritam Singh attended the Cabinet's swearing-in ceremony in 2011, he met then President S R Nathan.

A few weeks later, he received a pleasant surprise in the mail - a photo of him and Mr Nathan taken by the official photographer that night, with a note from the President wishing him the best.

Recounting this in a Facebook tribute to Mr Nathan, Mr Singh said: "I have come across some civil servants and state officials who by their actions and mannerisms, look down on Singaporeans who represent the opposition. President Nathan was not one of them."

Several opposition politicians yesterday shared on Facebook stories about their encounters with Mr Nathan, who died on Monday.

WP chairman Sylvia Lim said Mr Nathan and her father had been colleagues in the civil service. She added: "When I became Non-Constituency MP in 2006, President Nathan was very kind to me and generous with his precious time. He always made it a point to... say 'hello' and to ask how things were going."

Former NCMP Gerald Giam recalled him as a president who never rejected a call from a foreign dignitary, no matter how last minute.

Once, a request came in from a foreign dignitary who wanted to meet Mr Nathan that very morning. Mr Giam, who was handling the request as a Ministry of Foreign Affairs officer, said Mr Nathan agreed despite the short notice and rushed to the Istana for the meeting.

"Such was the nature of the man. He took his responsibilities very seriously, and carried our flag with much grace and dignity," he added.

Reform Party chief Kenneth Jeyaretnam said Mr Nathan had attended the wake of his father, the late opposition veteran J.B. Jeyaretnam.

"His family are in my thoughts at this sad time," he said.