This metal cage is the covering to an abandoned stairwell down to what used to be South Kentish Town tube station, which closed in 1924. It is now a pit collecting litter, while the beautiful building across the road, which was once the ticket office, is now a branch of Cash Converters.
I walk past this spot most days, and with more than a passing interest - in the spring I surreptitiously hung a hanging basket from the central strut above these bars, which has bloomed profusely all summer with red Impatiens (at least when I've watered it enough). This time I was wandering home from an abortive attempt at exercise with my flatmate, and we'd stopped to pour the contents of our water bottles into the soil. He is far taller than I am (I stuck a bottle to a stick for when I had to water it alone), so while he was drenching the basket unaided, I watched on and around and noticed this yellow below, matching the plasticked chain and the sign beneath. The plant flowers still, although surely not for much longer, for London grows autumnal, and Impatiens does not.
