Private detectives are traditionally instructed to get evidence of extramarital affairs. But for a growing number of Philic Man Hin-nam's clients, it's not their husbands or wives they want followed, but their children.
Suspicious parents call her in when they fear their offspring are involved with drugs or trading sexual favours for cash.
And more often than not, their fears are justified as Man brings home evidence of privately educated daughters taking drugs at yacht parties, or 13-year-old twin girls engaged in 'compensated dating' to buy designer label clothes.
Man, of Global Investigation and Security Consultancy, said there was a surge in the number of parents paying her to spy on their children.
While official figures suggest drugs and compensated dating offences have decreased, her experience suggests otherwise. Man said her company handled 298 investigations into children last year - a 68 per cent rise from the 177 cases in 2010.
In 155 of last year's cases, children were confirmed to be involved in compensated dating, a rise of 121 per cent. Another 120 cases revealed children were involved with drugs, up 34 per cent.