Lam Hung-hon, 52, and his Thai mistress Sinporn Srithamphong, 29, were jailed for 14 years and five-and-a-half years respectively by the Court of First Instance on April 28.

Lam was found guilty after trial of two counts of kidnapping an 11-year-old boy and his eight-year-old sister and for administrating a noxious substance on the former. The woman admitted to two counts of kidnapping.

They had been missing five days by the time the report was made, but officers still traced the culprits and rescued the hostages within a day-and-a-half.

Detective Senior Inspector/Regional Crime Unit/Kowloon West Dave Fremaux said it was extremely lucky officers could trace them so soon as the boy had been seriously injured while held captive.

"The young boy was in a very bad way as it looked as if something like chloroform was used to try and keep him quiet, but it badly burned his mouth and face and he is now scarred for life," Mr Fremaux said.

The drama started in Sham Shui Po on December 10 when the woman, their former maid, and Lam enticed the children with toys and sweets and took them to a hut in the New Territories.

The family received a ransom demand that evening and the money was paid on December 12 but by the 15th, the children had still not been returned. The family got worried and only then called Police.

With virtually no information to work on, detectives found the ransom money was being withdrawn from a bank account and the suspect was later identified along with his car.

The vehicle was found near the Yuen Long hut where the children were held - the pair were arrested.

DSIP/Crime/Ho Man Tin Edmund Tong Pak-sum, who was part of the KW team at the time and made the arrests, said he would never forget that night and the feeling of despair when he found the ill boy.

"We found him lying on the bed with bad wounds to his face and mouth which was also covered with adhesive tape. He had been burned and not given any treatment.We went to him but he could not speak because his mouth was all swollen up."

DCIP Matthew Kwok Ho-fai said the conference room which senior detectives used to co-ordinate the operation erupted into cheers and applause after the kids were found.

"There was a point when there was no communication with the officers, but when we finally got the call the kids were okay the whole room lit up!"

Superintendent/Crime/Operations/Kowloon West Stephen Lo Wai-chung, investigation head, said the case showed the importance of reporting kidnappings immediately to Police.

"If reported earlier, the children would not have suffered. Once the report was made, my unit and others co-operated and dealt with the case quickly and professionally. The public should be confident in the Police. The sooner they report the case the better. Thankfully this time, there was a happy ending," Mr Lo said.