Since Mr Ng started work at the ICAC in its first year, he has seen immense changes in public attitudes.

He smiles as he recalls how an early supervisor, Paul Dickinson, who was transferred from the police anti-corruption branch to the ICAC on its inception, suggested that the young Ng be dropped after his three-month probation, partly because of his poor English vocabulary.

But he was kept on largely because he spotted notes in Chinese on bank records when he and a junior investigator named Mike Rowse - now head of Invest Hong Kong - were probing a case. The suspect went to jail, Mr Dickinson and Mr Ng became friends and, to boost his understanding of English, the young man from a poor family took up Scrabble. He is now the ICAC champion of the word game.

Unlike many idealistic youngsters who thronged to apply for the ICAC because of the deep feelings stirred up by the Godber case, Mr Ng wanted to switch from the ambulance service because of the higher pay and status offered by the commission.

That changed in 1976 when he was working on a graft case involving Tsim Sha Tsui police.

'The entire police station shared the bribes which were organised, collected and distributed by the station sergeants,' he says. The system was universal throughout the force. 'There was a woman prostitute with four children, all by different fathers. She got $50 a time for sleeping with men, and $15 of that went to police and some to triads.'

The sordid tale of her life and how money-hungry grafters profited from her misery disgusted the young investigator.

'As an ambulance man, I got satisfaction from helping people,' he recalls. 'But as an ICAC man, I feel that I can do even more for society.

'That force is still inside me,' says the Buddhist. 'This is a great career.'

The biggest change he has seen in the three decades he has risen through the ranks is the vast shift in public perception. Graft, once an accepted part of life, has become 'intolerable and evil' in the public eye.

Because of constant vigilance and increasing public support there have been 86,082 complaints of alleged graft by the public since 1974. Corruption is now a high-risk crime, he says. If people are tempted, they realise they have to fear the scrutiny of the ICAC.

The biggest change has been in the police. Because of zero tolerance by a series of high-minded and determined commissioners, the culture of the force has changed. There is now no sympathy by police for brother officers who are caught on the take.

'In my early days, I would never tell people where I worked,' Mr Ng admits. 'Many people either hated or feared the ICAC. I told my immediate family where I worked but begged them not to tell other relatives.

'I kept it secret from all but my closest friend. It wasn't until the early 1980s that I exposed my real identity to friends.'

Now he is immensely proud of his job and people always want to talk to him about it. He is the centre of attention when there are reunions of the students of the Lok Sin Tong Free Primary School.

The veteran investigator says the major shift in attitude towards corruption is the greatest achievement of the commission.

'We used to be the capital of corruption,' he reflects. 'In one generation, we have educated ourselves to become clean.

'In another generation, we will improve even further. Now we're ranked 14th in the world as being clean. Give us another 30 years and we'll be number one.'