At the end of 2002, a few months after Stephen Lau Sing-hung moved from Hong Kong to Beijing to be the managing partner, northern China, of Ernst & Young, Sars struck the capital. 'It was scary. The streets were empty during peak hours. All the restaurants were closed and we couldn't find anywhere to go out for dinner,' he said. Mr Lau will retire at the end of this year after spending his entire career - 34 years - in accounting. He opted for the life of a low-profile tax expert, while his younger sister, Emily Lau Wai-hing, chose journalism and later entered politics to become one of Hong Kong's most vocal pro-democracy campaigners. Mr Lau joined the accounting industry in the early 1970s and became a tax partner at the predecessor firm of Ernst & Young in 1984. He had long been active in bringing foreign investment to China but his involvement deepened four years ago when he accepted Ernst & Young's offer to move to Beijing to oversee the firm's expansion there. 'The relocation came because of increasing demand on the part of our mainland clients, who wanted to expand or to list overseas, while our international corporate clients also had big expansion plans in China. These companies needed our auditing and tax advisory services and we had to be in China to get close to them,' he said. Mr Lau was prepared for life to be different in Beijing than it was in Hong Kong, but he had not expected that his first challenge would be a health crisis, rather than his halting Putonghua. As soon as Sars hit he called in the doctors to brief the staff about the disease and how best to avoid it. Contingency plans were drawn up in the event that the office building occupied by Ernst & Young had to be closed or that one of the staff would fall ill. 'It occurred to me more than once to go back to Hong Kong,' Mr Lau said. 'But I knew I had to stay on. China is a place of huge business opportunities and I had to be there to expand my company's business.' Fortunately none of Ernst & Young's staff contracted the disease. As the crisis subsided Mr Lau was able to focus his attention on business and sign up some big-name clients, including Industrial and Commercial Bank of China. Just how busy he has been in the past four years is borne out by the numbers. In 2002, the accounting firm had just 300 staff in Beijing. Today it has 1,600. Mr Lau also oversaw the establishment of Ernst & Young offices in Wuhan and Dalian, bringing its total in the mainland to 10. In China including Hong Kong, the firm has 6,000 staff and Mr Lau said that 10,000 was only a few years off. 'We recruit 1,000 fresh graduates every year so it won't take long for us to expand to 10,000.' A quick expansion of headcount was needed to handle the needs of mainland clients who generally are bigger than the firm's Hong Kong clients and often spread their activities across several provinces. 'I'll give you an example. The October listing of Industrial and Commercial Bank of China required Ernst & Young to send a 600-member team to audit the bank's nationwide branch network beforehand. It takes about 10 times more staff to service this one client than it does to service the average big Hong Kong company,' he said. While accounting firms can recruit juniors in China, senior accountants are rare in the mainland. Mr Lau said this meant there were good opportunities for Hong Kong professionals. 'Hong Kong is economically more mature than China but China is on a growth trend. For the accountants who want to make a career, it's a good idea to spend a few years in China,' he said. However, living in the mainland is by no means easy. Accountants stationed there must deal with executives and government officials who have little knowledge of international auditing practices. Day-to-day life is not as convenient, either. For example, Mr Lau is still afraid to drive there. 'The language is different. The food is different. Some provinces in China serve only spicy food and it's difficult for people like me who can't handle spicy food,' he said. Family strains can arise when husbands want to work in China but wives want to stay behind in Hong Kong. 'Parents must also consider where to have their children study. But China has some famous universities whose quality is not lower than that of universities in Hong Kong.' The key to working successfully in China, he said, is never to consider it a comfortable back-garden job. 'Some people think if they can't find a job in Hong Kong they can go and work in China as a second choice. In fact, it isn't true. You have to be a really good professional to be able to compete in China.' The potential rewards are great. Many headhunting firms say people with middle management experience in Hong Kong and the mainland are the most sought-after executives in China. Mr Lau has yet to decide what to do after retirement. Would he follow his sister into the political arena? 'Definitely not. Politics is not my cup of tea. I think I will take a break before I decide what to do next. Initially, I will spend more time playing golf,' he said.