I-OnAsia was set up with $2 million start-up capital in 2000. Mr Elmer, a Briton who came to Hong Kong in 1988, spotted the potential while using investigation firms in China during 10 years working for conglomerate CNT Holdings which had extensive mainland business.

'I saw the niche because often the information provided from China was of poor quality. I saw I could utilise my sources and turn that information into money and that's what I've done,' he said.

I-OnAsia's reputation grew rapidly and soon his rivals such as Kroll became his clients. 'They gave us work because we could get information that maybe they couldn't.'

But then came 2001's post-September 11 crash and Mr Elmer rued having so many eggs in one basket. Many of the firms who had been subcontracting to I-OnAsia cut costs by taking work in-house. 'We were left hanging because a vast amount of business had been coming from our competitors.'

He warned he would have to compete with them to survive. 'And we may bump into your clients who we have done work for in the past,' he told them. 'People soon realised we were the ones who'd been running around in China.'

I-OnAsia thrived by keeping costs down and providing the best intelligence. 'One of the reasons for our success is that if we can't do something, we will tell you,' says Mr Pengelly, the firm's director of investigations.

The industry is small but highly competitive and firms are only as good as their last job. 'If you are not making your clients look good, they won't come back', says Mr Elmer.

Although 70 per cent of his clients are Fortune 500 firms with Asia business, Mr Elmer keeps his eye on the bottom line, with modest offices in Kwun Tong. 'We like low rents. We don't need a gin palace.'

Historically, commercial investigation has been priced at 'an amazing level', he says. 'But we have brought it down to a logical, acceptable rate.' If the rest of the industry is less than happy at being undercut, the clients are not complaining, he adds.

With 95 per cent of the work in China, local and mainland investigators keep the wage bill down. 'We have made a point of not being expatriate-heavy. I am not going to send some [127 kilogram] former Hong Kong copper into China for a surveillance job. We believe in local people for a local job.'

With 100 staff and 12 offices worldwide, including four in China, growth has been steady. In five years annual turnover has grown from $3 million to $50 million, with profits ploughed back into the business except for a dividend Mr Elmer takes as major shareholder.

Macau's casinos are a steady revenue stream, as is a call centre there for US-listed clients who must provide an Asian language facility to log complaints.

Although much work comes from repeat business and referrals, the firm aggressively pursues new business, with a New York office focusing on intellectual property, brand protection and due diligence for mergers and acquisitions.

'We're probably the most successful brand protection firm in China at the moment,' says Mr Pengelly who specialises in tracking counterfeit syndicates.

His team has just closed down one of the biggest syndicates churning out fake Chanel handbags in south China, with 13 arrests.

Other successes include the seizure of US$5m of counterfeit goods for Cisco Systems, which shut down another huge syndicate and resulted in a judgment in Shenzhen that jailed four people for up to four years, the longest terms yet for intellectual property crime in China.

The stakes are high and the work often dangerous, with cigarette counterfeiters in particular prepared to stop at nothing to protect their expensive equipment.

Another reason for the firm's mainland success is that I-OnAsia supports and co-operates closely with the Chinese authorities, such as the Public Security Bureau and Technical Services Bureau, to fight intellectual property crime. They come in for undeserved flak, says Mr Elmer, who always ensures they get public credit for their successes.

'They appreciate that and deserve more praise.' They want to do a good job too, he stresses, and they really are sick of people whingeing about them, says Mr Elmer. 'In Beijing I've never seen such professionalism. They make their counterparts in many other countries look pathetic.'

The authorities are willing to help foreign brand owners but if a major case such as the baby milk scandal arises, they divert all their resources to it.

'Everything else was dropped and that was admirable - rightly, they prioritise,' says Mr Elmer, adding that in such situations his 60 mainland investigators assist, because nothing else gets done until the major case is solved anyway.

Getting information in China is easier if the authorities are on-side.

'In China, having relationships is key. With nurturing, people become our friends and we are not just using them,' says Mr Elmer.

As for I-OnAsia's future, there have been inquiries about acquisition but Mr Elmer has ignored them, preferring to think about expanding into Singapore, India and a small office in London.

'I really enjoy this business and I'm not really looking to sell. We just want to provide a service to companies doing business in the region who don't want to get burned. We're not money-mad,' Mr Elmer says.

But, he adds: 'If someone came along with a big cheque for silly money, I'd take it.'