A young foreign student snapped a shot of a group of students on a boat trip 30 years ago. Now he is back to find out what had happened to the lives of these students and their teachers. Wu Ni in Shanghai and Yan Yiqi in Hangzhou find out how he reconnects.

Thirty years ago, British photographer David Thurston took what he still thinks is his favorite shot. It was a picture of a boat carrying about 50 children on the waterways of Shaoxing in East China's Zhejiang province. The huge smiles on the young faces seemed to light up the ancient water town in that black-and-white photo.

Thurston's photograph of a happy class outing with about 50 smiling children and their teachers.

For years, Thurston had hoped to track the owners of those young faces and find out how their lives has been influenced by the dramatic changes which had happened to China in the past 30 years.

His wish was realized in May this year when the 69-year-old photographer finally stood on the same site and met some of the subjects in his photo.

Despite suffering from Parkinson's disease a few years ago, Thurston never forgot the scene where he took the photo.

It was in 1983 when he had just finished a course in Chinese art history at the China Central Academy of Fine Art, and Shaoxing was one stop in his ambitious trip across China.

Standing on a bridge not far from the former residence of modern Chinese literary giant Lu Xun, he noticed a boat passing under and someone on the boat called out: "Oh look, there's a foreigner!"

All the passengers on the boat looked up and smiled and Thurston pressed the shutter.

"It showed such spontaneous friendliness because I did not ask them to smile," he says. "Not everyone in China would smile at foreigners at that time and many were nervous."

Born in a family of farmers, Thurston was first attracted by China because of its "miracle of feeding a large population with a limited amount of land".

While he was studying politics at the London School of Economics and Political Science, the "cultural revolution" (1966-76) happened, which made him even more eager to know things about China. He learned Mandarin in Cambridge University for a year and then got the scholarship to study at the CAFA.

The "old China" impressed Thurston with big red slogans on the wall, men and women uniformly dressed in blue, brown and grey, and very nervous in speaking to foreigners.

He visited China for a few times after that and was amazed to find more shopping malls and more smiles.