There is one of these just around the corner from where I live.
It’s long, thin, green and old and thrusts straight into the air like a giant’s, er, finger. It’s not a telegraph pole – there are no wires coming off it – and it’s too tall to be a broken street lamp.
It is, in fact, a stink pipe, one of four such items of street furniture that can be found within a half-mile radius of Brixton Water Lane. These stink pipe were built around the same time as London’s Victorian sewer network in the 1860s and are basically just huge hollow pipes that allow potentially lethal gas to escape into the atmosphere, far above the rooftops. They often seem to located near the locations of culverted rivers – these ones are found more or less on the route of the Effra or its tributaries – suggesting that when these rivers were incorporated into the sewer system, they required some sort of additional safety valve (the buried Fleet famously exploded at King’s Cross after just such a build-up of gas in 1846).
Some stinkpipes are rather elaborate, but the ones I’ve seen around Herne Hill and Brixton are pretty basic and utilitarian. If you want to find some finer examples, like the fine crowned stench pipes of Kennington Cross, you should check out the excellent London Stench Pipes blog, which is devoted to these marvellous oddities leftover from Victorian London.