In a letter to the Commissioner, Deputy District Judge Colin Mackintosh said he publicly commended SPC Yeung when convicting two ringleaders and seven members of the gambling syndicate of a charge of conspiring to operate a gambling establishment on Apleichau Estate in Aberdeen.

"He must at times have feared for his personal safety. He was working alone in the field, in what was to him a potentially hostile environment. He carried out his duties with conspicuous dedication and success, and he is to be commended to the Commissioner of Police," said Judge Mackintosh in his letter.

Mr Mackintosh jailed the nine defendants for eight to 18 months. He discharged the tenth defendant, giving him the benefit of doubt.

It was by sheer coincidence that the Regional Anti-triad Unit of Hong Kong Island Region picked SPC Yeung early last year for his undercover duties. At the time, the unit was planning a special operation to smash a syndicate, which had been operating the Russian poker card game (locally known as "sap sam cheung") at the sitting-out or open areas on Apleichau Estate for some time.

The unit was also looking for an officer who would act as an undercover operative to identify the core members of the syndicate, and ascertain its modus operandi, scale of gambling activities and the roles of each core member.

"We wanted to secure evidence that could drive a nail into the syndicate's coffin with charges carrying heavier penalties. The candidate we had in mind was an officer who could pass himself off as a resident of the estate and took part in the card games without arousing the gangsters' suspicion. We also expected the candidate to have experience and know how to react to sudden changes. We would provide all the necessary training for the candidate," said Acting Chief Inspector Yeung Yiu-chung, who is in charge of the anti-triad unit.

The job of finding the candidate fell on the shoulders of the unit's Detective Sergeant Wong Chi-nang, who had spent many days, observing officers changing their shifts at various police stations. Subsequently, he spotted SPC Yeung at Chai Wan Division and identified him as the qualified candidate.

"Mr Yeung Siu-kwong's appearance, age and working experience fitted our requirements. He has an ordinary look but in fact is quite smart!" said DSGT Wong.

What followed were briefing and intensive training for SPC Yeung who was full of confidence when he began his undercover mission.

Having successfully "integrated" into the estate community, SPC Yeung subsequently observed that illegal gambling activities took place on a total of 20 occasions at three different locations from 10 am to 7 pm between February and May 2005. The operation turned overt when officers of the Regional Anti-triad Unit and the Regional Special Duties Squad apprehended eight syndicate members and 23 gamblers during a raid on an open area on May 10, 2005. Two more core members were later arrested elsewhere.

SPC Yeung describes his undercover job as "a very good experience". "Inspector Yeung and Mr Wong have taught me a lot of skills for the operation. I've also learned things that I've never come across as a UB officer," he noted.

Acting CIP Yeung said he was pleased that the court had accepted evidence that the syndicate's gambling activities were more than street gambling, and that the court was satisfied that the syndicate had regularly operated a gambling establishment in an organised manner, depriving the public of the use of the areas where the illegal activities were carried out.