By looking around the web it is saying anything connected before the master socket is illegal. I notice there is an extension connected at the junction box where the line enters the building. As openreach put a new filtered faceplate on the master socket will this extension cause interference to the VDSL signal?
I also see that you can use an ethernet cable from new filtered master socket to the router as long as it's under 100 meters.
I am not fussed about this extension that's from the junction box as I don't use it - however if it would be an issue it will have to be removed.
Thanks in advance.