This rather quaint abandoned street light...
In the last few months the bracket mount has given way and the bracket is now hanging loose off the column.
I wonder who's responsible for it? :?
It is a shame this lamp has been allowed to decay almost unnoticed (except by yourself).
Looking at the GSV suggests this column is on private land, rather than some long forgotten council relic, however I can't decide if the lawned area is part of the property or is is a utilities strip (for cabling / gas / water etc).
I noticed the lamp's junction box is empty apart from the feed cable to the lantern. If it was an original installation (even long out of use), you would expect to have a evidence of a fuse or cutout inside.
As to why it was erected here in the first place, the most logical one would be it was put in by the property owner, many years ago. That said, it seems odd as to why the column has been left derelict, when the house itself is in a good state of repair (even the front lawn is nicely cut).
Another possibility, is that the column may in fact have nothing to do with the relatively modern housing which surrounds it. It could be the lamp was here long before these properties were built. There may have been previous buildings here along with the street lamp, until the site was cleared for redevelopment. A chat with the owner or landlord for these properties (assuming they are leasehold) might indicate who the column belongs to now.
What I have noticed with demolition sites, is that buildings are knocked down without a thought, however if a streetlamp happens to be on the same site, it is usually left standing. Perhaps the demolition crew mistakenly believe it is still live or even council property. It makes you wonder therefore, if your lamp avoided being pulled out for this very reason.
Anyway, so much for a quick answer!
In the first instance, I would suggest that your first port of call, would be a friendly chat with the owner of the house (closest to the column itself). If they own it, they may well know of its history and hopefully be aware of its increasingly perilous condition. If they do not own it, they may well know who does. It might be the council after all or even a utility company.
It might be that the person you speak to might simply be renting the place, therefore you would need to contact the property owner (perhaps liaising with the tenant or property management company).
Assuming this does the trick, I'm sure you will be able to decide between you the best course of action for the continued interest in the lamp. I myself would be quite happy to save just the swan neck and lantern if I could (even if it potentially means sourcing a repro' gas lantern to replace it with).
Hopefully the bowl hasn't been damaged following its collapse. I wish you luck in hopefully saving it.
Before I forget, I do recall there is some useful information regarding this sort of thing in the "guidance for collectors" tab at the bottom of the Ukastle pages. The section on "abandoned property" is particularly appropriate here.