SINGAPORE - He was hoping to spring a surprise on his son, but ended up facing an even bigger surprise himself.

Mr Keith Goldfinch, a British engineer at Rolls-Royce, had just returned to Singapore from France on June 19, and decided to make an unannounced trip to pick up his four-year-old son William from nursery school.

"I was feeling jet-lagged… (and) in a daze," he recalled.

The 42-year-old travelled to Newton MRT station and just as he had stepped onto a downward-travelling escalator, he was jolted by shouts for help to stop someone from two girls on the adjacent escalator heading upwards.

Mr Goldfinch then saw a man rushing down the escalator in his direction. When he grabbed the man, the latter denied any wrongdoing and struggled to get away.

"I was worried that we will fall down the escalator and get hurt," said Mr Goldfinch, who suffered a minor graze on his leg during the tussle.

Another commuter eventually assisted him in restraining the man.

The 53-year-old suspect was arrested and is currently under investigation for allegedly filming upskirt videos of a female commuter.

Mr Goldfinch was awarded the Public Spiritedness Award by the Singapore Police Force (SPF) on Monday (June 25).

Police figures showed that last year, there were 447 reported cases of insulting the modesty of a woman, compared to 531 in 2016.

The crime also includes acts like taking bathroom videos, indecent exposure and verbally insulting the modesty of a woman.

"Currently we don't see an increasing trend… in terms of the number of (upskirt video) cases we have... it is not a particular concern… but I think for the victims, every case is one too many," said Commander of Public Transport Security Command, Assistant Commissioner of Police Koh Wei Keong.

He urged women to be more careful when travelling on escalators, a hot spot for reported incidents.

Mr Goldfinch was modest about his good deed.

"I don't feel like I've done anything particularly special… I've done what anyone else will do, it's an instinctive, human thing to do. If I haven't done anything, I would have felt awful," he said.

But his wife Rachael Halliday, a 43-year-old associate director at KPMG, and four-year-old son William think otherwise.

Ms Halliday said the Father's Day card they prepared for him best expressed their feelings. On it was the message: "You are a hero, daddy."