I could spend my spare time reading an improving book. Instead I find
myself wondering why do some escalators have the handrail running
slightly faster than the steps? I've noticed this on and off over the
years, and currently am most aware of it on the Jubilee line
escalators at Westminster. If you step onto the escalator at the
bottom and keep holding the rail, then by the time you reach the top
your arm has been pulled about 18 inches forwards relative to the rest
of your body!

Assuming the same motor drives both the handrail and the steps, I
would have thought it takes some quite complex engineering to achieve
this feat. Why???