Just experienced second occurrence in Waterloo station, of all places. I found out it used to be a marsh and pleasure garden, frequented by thieves and pickpockets(the garden, not the marsh), before it was a train station. Also the marsh was fed by the Tyburn river, which ran past the famous site of execution, Tyburn hill(not sure how a river from the north side of the Thames feeds a marsh on the south side). Also the marsh was owned by the Earl of Arundel, who was attainted and died while imprisoned in the Tower, he was canonized in 1970 as a catholic martyr(Phillip Howard, 20th Earl). I guess iron is not all it is cracked up to be as regards the ffayre-ffolke. Or maybe steel is somehow exempt. My head is still spinning.
Also missed the obvious the first time i wrote this(pleading special circumstances). The Thames is a liminal water par excellence. Continuously inhabited for close to 12,000+ years, a couple thousand for London alone.