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That is an old DACS unit which may still be needed, although most of them should have been recovered by now, unless there is a dire shortage of cable pairs to your area.
It Openreach who would have to deal with that, but you will need to make the request via your phone service provider.
Ask them to arrange removal of a DACS unit.
If all else fails, you may be able to place a request directly to Openreach, using this form, if its outside.
Huge thanks for the advice and apologies for the delay in replying/acknowledging. The service is now provided by Chess Telecom so I'll contact them The unit is indoors.
I messed up on the 'ticking who solved it' part
Full credit to you