SINGAPORE - It began with a casual conversation among a group of St Patrick's School old boys last December, but ended up becoming an exhaustive attempt to track down as many batchmates and teachers as possible for a 50th anniversary reunion.

Some had died, others had seemingly vanished without a trace, and a number declined to turn up for professional or personal reasons.

In the end, more than 50 St Patrick's School alumni from the class of 1969 gathered at the Singapore Cricket Club on Thursday (Aug 15) to thank 13 of their teachers for helping shape them into the men they are today.

"It was a time-consuming and occasionally distressing undertaking. I tried to contact 130 of us and 15 teachers in all, and some had passed on or were down and out," said engineer Wesley D'aranjo, 66, chairman of the organising committee and retired brigadier-general from the Singapore Armed Forces.

"But it was worth the while since we are only here because of the teachers. In those days, we were called the 'best school in the world' by the waterfront because St Patrick's had a reputation for gangsters, and the brothers (the Catholic clergymen who served as teachers) were the ones who controlled the situation," said Mr D'aranjo.

Mr Coleman Baptist, 83, was one of the Catholic clergymen who taught generations of students at St Patrick's School over four decades. He joined the school in 1965, leaving to teach at another Catholic school, St Joseph's Institution, from 1972-1982 before returning to St Patrick's until his retirement at 80 in 2016.

Brother Coleman, as he is known to his students, was the man behind St Patrick's emergence as a football powerhouse in the 1960s and the annual inter-class football league.

He was a vigorous football player himself and was so fit that "if you knocked into him on the field, you fell down", said Mr D'aranjo.

Mr Baptist, who taught English and history, said: "I have no children but I would always say, if someone asked, that I have 40 children every year. The pupils are my children."

He recounted vividly the story of one student in 1969 who had been dumped by his girlfriend and threatened to jump from the third floor of the school building.

This was before Catholic Junior College was formed and co-ed pre-university classes had been introduced with some female students from the Catholic convent schools joining their male counterparts at St Patrick's.

"The other boys were egging him on to 'jump, jump, jump'. Of course he didn't jump, he just wanted to show the girl how brokenhearted he was," said Mr Baptist.

St Patrick's School was established in 1933. Notable alumni include Singapore's seventh president Tony Tan, former Cabinet minister George Yeo and diplomat Barry Desker.

The class of 1969 produced a President's Scholar in Mr D'aranjo, 1973 SEA Games judo champion Choo Kah Wah, former national footballer Brian Batchelor and former Straits Times journalist and associate news editor Paul Jansen, among others.

Mr Jansen, 66, who was at the reunion, expressed regret that he was not able to show his appreciation to the teacher who made the most impact on him.

His former literature teacher Mabel Tan had encouraged and nurtured his love for writing, which later led him to journalism.

He did not manage to meet her again before she died more than 15 years ago of cancer.

"She was loud and demanding and pushed us right to the wall and over it. But she had a heart of gold and would dig into her own pocket to fund our class activities," said Mr Jansen.

"So my message to all students out there is: if you've had the good fortune to have teachers like we have, don't wait until it's 50 years down the road to let them know how grateful you are."