His first venture - and first business mistake - was Tsim Sha Tsui's once celebrated Tartufo restaurant, which closed in 1993. Though busy when it first opened in 1989, it quickly drained cash - something Mr Louey blamed on a combination of 'an inconvenient location and spending too much on decoration, cutlery and expensive staff to sing opera'.

What he learned: 'One should never set up a business you don't know. And if you do start one, find a good partner who has the expertise. I had thought running a restaurant was easy. It looks like all you need to do is move in the tables and chairs and buy knives and forks.'

He also oversaw production of the finale of Tsui Hark's A Chinese Ghost Story trilogy, released by his family's film studio, Golden Princess. Later, he worked on property projects, including the Pioneer Centre in Mong Kok. However, both the film and property firms were sold in the mid-1990s 'because they didn't have very good results'.

Finally finding a good partner, Mr Louey invested HK$40 million in 2001 into the small private construction outfit founded 40 years earlier by Ko Chin-fung. Combining the deep pockets and contacts of Mr Louey with Mr Ko's background turned Geofiber into the firm's key income driver. Within two years, Mr Louey broke even on his investment. 'We have the products and right people and right strategy,' he said. Indeed, in hilly Hong Kong, slope protection is big business.

Mr Louey said a major challenge was to convince the city administration to change from using the traditional concrete-based method for slope preservation to something that was both environmentally and aesthetically more pleasing. So far, of the thousands of steep slopes in the city, he has been able to push through more than 100 Geofiber projects. 'Hong Kong is an advanced city but the environment is not high up on the list,' he said.

Mr Louey is as candid about his mistakes as he is about the irony of someone peddling environmental solutions also being a non-executive director of KMB operator Transport International Holdings, frequently a target of complaints by green groups for its buses' air conditioning being to high and the vehicle emission standard too low. 'We discuss it a lot in directors' meetings and try to do everything to eliminate pollution,' he said. 'But if our 4 million daily passengers each drove their own cars, it would be worse.'

With one business success under his belt, Mr Louey has been looking to expand his horizons. Last year, the Geofiber company made a net profit of 'a few million', which he reinvested into research on building what he would only describe as 'green housing', and gave to charity.

Giving to charity contributed the most 'to my happiness', he said. His focus is mainly on the William SD Louey education foundation, which he set up in 1995 in memory of his grandfather, who started the bus company in 1925.

Since its inception, the fund has spent more than HK$52.5 million sponsoring at least 35 talented Hong Kong and mainland students, at about HK$1.5 million each, to study in England and the United States from about age 13 until graduating from university.

'I am lucky to have been born in a nice family and I wanted to give back to society,' he said.

Taking it a step further, Mr Louey plans to bequeath all his considerable wealth to the educational fund, leaving not a cent to his now-teenaged children - a musician daughter, and a son who is a member of Hong Kong's ice-skating team aiming to go to the Vancouver Winter Olympic in 2010.

'I told them I will only provide them with a good education but then I would like them to be self-made,' he said.

'I was brought up by parents who did not push me to achieve, which I think led to my lack of drive. Now I am bringing up my children in a different way.'