Travelling home from Central London last night made me think of the journey as a whole. Over 100 miles in 1hr, 20 minutes just wafting along was quite some achievement I thought, especially as we made a couple of stops on route. It made me think of the power involved in getting the train to move along. The train was an intercity 125 with two power-cars. So if it can do 125mph with both engines running, how fast can it go with only one.?