It would take about 10 hours by air, but as the crow flies from King's Cross to Beijing is an ambitious plan pushed by China along with India. A train that travels nearly 400km/h was unveiled recently in China, linking Wuhan and Guangzhou. The hi-speed rail network will have trains travelling up to 322km/h. It all sounds super-scary fast thought. The Eurostar and the Shinkansen can go to 300'ish km/h. Hmm, those are pretty fast as well, and I've been on the former and you don't normally feel the speed, although would going an extra 100km/h be comfortable on a train?