AIn article , Bert
Coules wrote:
Currently, the incoming phone cable terminates in a small junction box on
the front wall of the property, from where a separate cable runs some
thirty feet to the master socket. The phone and wired router are both
located on a desk very close to the master socket.

The builders doing some renovation work on the house have suggested
putting the master socket on the front wall and then running two cables
to the desk area. Is there any technical reason why that shouldn't be
done? Will the internet performance be affected if the router is
further from the master socket than it is at present?

all the cabling before the master socket (and the socket itself) are the
property of BT. You (or your builders) are not allowed to alter them.

--
from KT24 in Surrey, England