Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
No, we are in a tube train here, the momentum moves it down a hill (as TPE said), but how does it get ABOVE ground, rather than underground? Note, I gave away the answer in this explanation, so see if you can get it.