[boudin]

Since it's a train in which you can walk from the last to the first carriage, he counted it as walking by walking the train while the train was going between Moorgate and Barbican. I guess technically it is walking and being underground.

[carnitine]

I can walk from Paddington to Canary Wharf underground if I’m allowed to pace up and down the train.

[petercooper]

I could walk from London to New York if the stewards weren't so touchy during take offs and landing.

[LadyCailin]

You could still do it if you define walking as “moving your feet constantly”, who cares about word definitions anymore.