I admit I was never very motivated to learn languages at school, and always assumed I was simply not good at them. So my friend's advice was encouraging six months ago, when I set about teaching myself some Putonghua before starting my 5,000 kilometre winter walk from Mongolia to Hong Kong. I was also encouraged to learn that research has shown that, for an English speaker, learning to speak Putonghua is only 20 per cent harder than French (although writing it is about 500 per cent harder).

My expedition partner, Leon McCarron, and I have completed our first month hiking south through the desert. As well as coping with some extreme cold on the Gobi trek, and enjoying some extraordinary hospitality from both Mongolian and Chinese desert dwellers, we have spent many, many hours just walking. The rather unglamorous side to expeditions is boredom with one's own company. But I am determined not to take for granted that we have an abundance of thinking time - a rarity in the hustle and bustle of Hong Kong. I have also had time to practise my Putonghua by listening to lessons as I walk.

This past week, our steady schedule of 30 kilometres a day brought us out of the desert emptiness and into a wide valley of busy roads, a double rail track, and increasingly prevalent industrial factories and mines. To avoid the roads, we have sought out little snowy tracks through the fields, which are what I dreamed about when I decided to cross China in winter on foot.

Walking is quite a contrast to my previous expedition by bicycle - cycling is much easier and faster, but forces you to stick mostly to roads. It has been thrilling to walk through a world of vibrant farming communities with villagers bustling around and shouting questions at us, while pigs lie sleeping and snorting beside huge haystacks, and flocks of tiny birds flit between the trees.

But the surprises of new China keep coming. Just beyond one village we came to a giant construction site of half-built compounds. A billboard showed what it would become: a huge new town, complete with parks and a power station.

As we encounter more and more people, there have been plenty of opportunities to use my Putonghua - and alongside the strategies of 'vocab' and 'repetition', I have also added 'being prepared to make lots of mistakes'. The Chinese are proving patient teachers, always working hard to figure out what I am saying; and, little by little, I am improving.

Last Tuesday evening, we crested a hill and before us was the incredible sight of the first proper Chinese city: Jining. As the hazy dusk sky turned from pink to purple behind it, we stared open mouthed at the vista of spewing chimneys, half-built apartment blocks, dazzling lights and fuming traffic. Before us, China's industrial revolution was in full swing. We took the next day off to explore the city.

We have now entered a new stage of the expedition, and the desert is behind us. More and more cities lie ahead, each one bigger and increasingly busy. But there will also be more off-road tracks and snowy villages, and impressive mountains.

This week, we are due to breach a Ming dynasty section of the Great Wall (although by all accounts, it is a small and rundown part, so we may have our work cut out to find it). When we reach the Great Wall, we will take a week off in the nearby city of Datong for Christmas, and my wife is coming to meet me. After that, we're back on the road, and we'll follow the Great Wall until we meet the Yellow River, then we'll turn left and follow it south.