He was described as a "quiet chap" when he was a student, first at Raffles Institution (RI) and later at the then University of Singapore.
Aravindan Balakrishnan, 73, was arrested last week for holding three women as domestic slaves in London for 30 years.
When heart doctor Low Lip Ping read the news, he thought it could be the same Aravindan who was his classmate in Form Two at RI. Form Two was the equivalent of today's Secondary One.
"But then again, it could have been someone else with the same name. Aravindan was as normal as any Form Two boy. There was nothing unusual about him then," Dr Low said.
Aravindan, who is reported to have been leading a Maoist "cult", had his Singapore citizenship - which was registered in 1960 - revoked in 1977. By then, he was already living in London.
Singapore's Home Affairs Ministry had accused him of engaging in "activities which are prejudicial to the security" of the country, after he was named a radical "closely associated with Eurocommunists".
Another one who "vaguely remembered" him was former People's Action Party Member of Parliament for Ang Mo Kio GRC Lau Ping Sum.
They were in the same year in the Arts faculty of university.
"I didn't know him very well as I did not get to talk to him. He was small in stature and did not say much in class," Mr Lau told The New Paper.
As the number of university entrants was small, The Singapore Free Press used to list the names of candidates selected for tertiary education.
A check of the April 7, 1960 issue found Aravindan listed among those entering the Arts faculty.