If the lamp post is an exposed-conductive-part then it is NOT totally isolated but It WOULD be better IF it WERE.
Look, I think it is agreed (apart from Bernard who thinks everything is) that the OP's box is NOT an exposed-conductive-part therefore earthing is not required.
The other option is, is it an extraneous-conductive-part which requires bonding? The answer is NO, it is outside therefore there are no exposed-conductive-parts of the installation which are simultaneously accessible.
The best advice is to ensure that the box remains isolated.
I am surprised no one has suggested TTing the socket. That doesn't mean I think it should be.
Look, I think it is agreed (apart from Bernard who thinks everything is) that the OP's box is NOT an exposed-conductive-part therefore earthing is not required.
The other option is, is it an extraneous-conductive-part which requires bonding? The answer is NO, it is outside therefore there are no exposed-conductive-parts of the installation which are simultaneously accessible.
The best advice is to ensure that the box remains isolated.
I am surprised no one has suggested TTing the socket. That doesn't mean I think it should be.