It's not strictly allowed, but it's been known to be done.
If you're running cables into the loft then back down to where the
socket is now, why not just run a extension from the master into the
loft, following the route from the master up to roof so there are no
extra cable runs. Or am I missing something?
..

SJW
A.C.S. Ltd.

As the cable is coming from a telegraph pole and therefore arrives at roof
level is looks unsightly running down the wall and worst of all wrapping
around the brickwork at the front door.

Typical BT job then! How about if you just tidied up the existing
cabling.
...

SJW
A.C.S. Ltd.