We seriously considered travelling all the way from UK to Beijing by train but were then put off by the thought of the length of the journey and particularly across Russia when much of the trip would have been through forest. In the end we compromised by flying to Irkutsk for Lake Baikal and then caught the Trans Mongolian into Mongolia where we broke journey for a few days in Ulaan Baatar before catching a train to Beijing.
We talked to various travel companies about the journey and one recommended if wanting to do the full journey to start in Beijing as we would be recovering from jet lag on the way home.
Joining at Irkutsk meant we were breaking into a group of people who had become good friends since Moscow. There was a lot of card playing and drinking... The train (and restaurant) work on Moscow time. Crossing the borders is an experience. BE WARNED toilets are kept locked until you are well into the next country. This can be several hours... Going out of Russia our compartment and luggage was given a very good going over (more so than entering Russia). The visas of two young men on the train had expired a couple of days previously. They were frogged marched off the train, fined 2000 roubles and told they would have to go to Ulan Ide to get new visas before being allowed to leave Russia.
The crossing into China is interesting as the train has to be taken into the workshops as the rail gauge is different between Mongolia and China. The carriages are jacked up, bogies are removed and replaced with bogies for the Chinese gauge.
It was an epic journey and we really enjoyed it but I’m glad we only did part of it. We travelled end of April. I can imagine it will be a magical journey in winter although with limited day length.
My review can be found here:
http://www.silvertraveladvisor.com/review/specialist-holiday/148744-review-trans-mongolian-railway
The pictures for the stretch between Irkutsk and Mongolia are here:
http://wasleys.org.uk/Asia_websites/asia_08_mw/01_siberia/05_TransMongA/index.html
The pictures from Ulaan Baatar to the Chinese border begin here:
http://wasleys.org.uk/Asia_websites/asia_08_mw/02_mongolia/01_UB/image-html/IMGP6127.html