The cage-like structures commonly seen in UK
I firstly noticed this kind of structure a few years ago in Google Earth and the movies of Alfie(1966) and Melody(1970), it can also be seen anywhere in the present version of Street View of Google earth. And at this movie, I also found 2 scenes having shown this kind of round metal cages, I recalled some posters of GooleEarth forum told me the cages were kind of oil tanks.
Can any British confirm and suffice my curiosity as what exactly are the cage-like structures used for ?