JohnP wrote

(are they still called that) BT Openreach have been doing some
work in my area (Fibre?) and on my daily walks I have noticed
some poles have at the base a 20mm diameter rod or tube abutting
the post with about a foot above ground and a metal staple holding
it against the post - and a rubber or plastic cap on it.

Has anyone noticed the same and has any idea what it could be?

It’s the new surveillance cameras and you will be summarily
hung, drawn and quartered for spilling the beans, you bugger.