But Dykes has been walking solo since late October, when the last of those accompanying him quit. Along the way, one by one, they quit because of severe altitude sickness, injuries or the fear of the multitude of dangers, including bears, wolves, winter storms and intimidating terrain.

In early October in Yushu, Qinghai province, British photographer Martin Lyons decided to withdraw from the adventure after an encounter with a big landslide in the mountains on the first day of his journey.

"It's pretty scary. One step wrong and we wouldn't end well," the 41-year-old man recalled their climbing on the cliff of the mountain that day. "Ash is an extremely strong person both physically and mentally. I have a lot of respect for him."

The world's third-longest river stretches about 6,400 kilometers from the glaciers of the Qinghai-Tibet Plateau eastward through the cities of Chongqing, Wuhan and Nanjing before reaching the East China Sea in Shanghai.

On that journey the entire length of China's Mother River Dykes is expected to walk about 8 million steps. "There are very few world records left to be challenged nowadays," he said.

Born in the town of Old Colwyn in northern Wales, Dykes has achieved two world-first feats, trekking across Madagascar and Mongolia alone without outside help, during which he nearly died from malaria and severe dehydration. His book Mission Possible was published in Chinese in June last year.

"Many had warned me before that it was impossible to walk the Yangtze from the source to the sea," he said.