The author lost me when they took a train from Moorgate to Barbican. Clearly doesn’t count as walking underground!
> It's taken 20 minutes to get here via seven escalators, two staircases, one ambulatory train ride and one lift. You may quibble that the train ride was a cheat and that a couple of bits weren't technically below ground, but you can't argue with the extraordinariness of such a long artificial subterranean connection.