"It is without a doubt the Mail Rail sits at the throne, laughing maniacally at the puny adventurers unable to even stare it in the eyes without bursting into flames, the pinnacle of exploration in London, if not England. There is, and will never be anything like it again, its uniqueness "forever unrivalled, London’s final unconquered “Grail” now a slain beast.

"So the Russians erected autonomous nuclear-powered lighthouses. Which worked great, until the collapse of the Soviet Union. In fact, they probably would have been fine after that, if people hadn’t looted them for copper and anything else that looked like it wasn’t nailed down too hard. Including, apparently, reactor shielding."