After a number of years lecturing abroad in Britain, the United States and Singapore, he returned to Hong Kong in 1999 to work at Chinese University's school of architecture.

More importantly, he is a man who likes to be kept busy. If he's not in his office or lecture rooms on the CUHK campus, he's likely to be found building a bridge in some faraway village in northwestern China.

It all began in 2002.

Shocked and distressed by a news broadcast about children from the village of Maosi, Gansu province, living in appalling conditions and risking their lives to cross a raging river to go to school, he decided to do something about it.

"Gansu is really the cradle of Chinese civilisation," he said. "China, as a race, originated here. So, culturally, it has a huge significance in Chinese history. But it's also a place of great poverty and deprivation.

"Initially, in 2002, I led a group of [Chinese University] staff and students there to try build better houses and schools for the villagers. But we found that river crossings were also a problem and the makeshift bridges that had been built were not good enough. They'd get washed away and people would get killed. It was then that we started to design our first bridge."

The project, named "A Bridge Too Far. A Dream Comes True" and officially launched in 2003, aimed to build a bridge for the Gansu villagers with the help of student volunteers.

Ng used his study leave to go to the mainland, speak with local officials and sort out logistics.

It was a laborious process but, in 2005, the bridge was built.

At 85 metres, it turned out to be the longest bridge Ng's team was to build.

More than 50 volunteers from Hong Kong built it in six days at a cost of HK$500,000 and, in 2006, it won the Royal Institute of British Architects' International Award.

"We called the project 'A Bridge Too Far' because it was our first project of this kind and it could have proved to have been just that," he said. "But we also called it 'A Dream Comes True' as this is what it would have been for the people of Gansu if we could do it. But it was clear to us that our work was just starting."

Ng next set up the Wu Zhi Qiao (Bridge to China) Foundation in 2007. In Chinese, "bridges that never end". It was the start of a journey that achieved a huge amount in the years since.

Under the auspices of the foundation, 28 Wu Zhi Qiao projects have been completed so far in Shaanxi , Sichuan , Gansu, Guizhou and Yunnan . The foundation also launched post-earthquake reconstruction projects in Sichuan and Qinghai .

"We set up the foundation so the work could be done more systematically and by making it a registered charity, with more people involved, it would be a better way to raise funds," Ng said.

"Our method is to design very simple, low-cost bridges and enhance the very basic ones that villagers have made. But what's more important is that we are planting a seed in people's minds and showing what can be achieved very simply."

Up to now, the Wu Zhi Qiao projects alone have helped more than 40,000 people living in rural areas.

In addition to the convenience and safety brought about by improved access, the projects have shown these villagers the care and compassion their countrymen thousands of kilometres away have for them.

Ng also started another initiative running in parallel - called "A School To Learn" - in Guangxi, helping build schools and other essential infrastructure.

But he is not about to sit back and admire his work - he wants to make a difference on a much larger scale.

"There's plenty of work still to do. Helping 40,000 people is nothing when you compare it to China's population. It's tiny. The work has just begun, but hopefully it will continue long after I'm dead and gone," he said.

" basically means never-ending bridges, and that's the ethos behind this project. That's why we bring students in to inspire them to continue the work that we have started, for generations to come."

Each individual project sees Ng liaising regularly with the Ministry of Construction, which then lays out a mandate and gives preliminary instructions for Ng and his team to follow. During all this the biggest problems to overcome are local politics and red tape.

"In the past I've called some projects 'Mission Impossible'. Not because of the technical side, but because of the human and political issues that can be involved," he said. "For those who want to do things in China, you must bear this in mind."

"But somehow these problems can be overcome, generally because in Hong Kong we have a 'can-do' spirit. The harder the job becomes, for whatever reason, the more determined we are to get it done thanks to this 'can-do' spirit."

At the moment, the 52-year-old is researching a book about sustainable urban design. This carries on from Ng's work as an environmental consultant to the Hong Kong government, where he helped develop the performance-based daylight design building regulations, and technical guidelines for air ventilation assessment.

Recently, he has been drafting "urban climatic maps" for city planning for the governments in Hong Kong, Singapore and Macau, as well as a number of mainland cities. And, as if this were not enough, he is also an international expert adviser to the US Department of Energy's initiative on "cool cities".

"There are not enough hours in the day sometimes," he said. "On some occasions my wife is lucky to see me a few times a month. But she understands that at times my work can be like this."

True to form, Ng has yet another initiative up and running. This time he is seeking to improve the lives of the poor and needy in isolated mainland villages by pooling the resources of universities in Hong Kong and the mainland.

The "One University - One Village" (1U1V) project seeks to get universities nationwide to work with people in remote villages to help improve their situations in any way they can using the universities' knowledge.

This venture aims to help villages in a multidimensional way - not just by improving their infrastructure, but by also helping them develop on an economic, social, ecological and environmental level.

"I'm absolutely certain that a university like Chinese University, with 10,000 people, can help a village of 1,000 people," Ng said. "With the expertise, knowledge and student resources available, I cannot see why this can't be done."

In the meantime, thousands of bridges are still needed on the mainland, and Ng will not be able to build them all in his lifetime. Neither will his students. It will take the effort of multiple generations to get the job done.

"Fundamentally my skills are useful for those who are in need and, more importantly, for those who are forgotten. The message is that we don't have to do much to make someone else's life better," he said.

"If everyone can do one simple thing, it'll make a difference. It's not a matter of doing big things. Don't underestimate the importance of doing many small things well.

"It will all accumulate into something useful, and future generations will make sure this work continues to go on. That is my dream."