The finger in the dyke...
Todays shot is of the one thing that keps London going, the Thames Barrier.
The Thames is a tidal river, and the effect of the tide is magnified as the river progressively narrows going inland, by the time the river gets to London there can be up to about 30' of difference between highest and lowest tides. Walking along one of the Thames pathways with the river level at pavement height is a disconcerting experience.
In order to prevent London flooding, the Thames Barrier was built. When it was conceived in 1966 it was expected to be raised once every six years. It was opened in 1984, and now it operates six times a year. Climate change is real, and it is here.