When a group of Chinese cyclists threw a stray dog a bone, little did they know that they were at the start of an epic journey that makes Lassie Come Home look like a walk in the park.

The cyclists, on a 1000-mile (1600-kilometre) expedition from Chengdu to Lhasa, came across the small white mongrel in the mountains around Yajiang, a Tibetan area of Sichuan, five days after starting out.

One of the riders, 22-year-old Xiao Yong, tossed the dog a chicken drumstick. To his surprise, it began to follow them - and stayed the course for 20 days to become a sensation in China.

The dog - since named Xiao Sa, or Little Sa - climbed 12 mountains higher than 13,000ft, and stuck with the group during heavy storms. Indeed, as cyclist after cyclist dropped out, exhausted by the steep mountains and the thin air of the Tibetan plateau, the dog kept him and his colleagues going, said Mr Xiao.