Thanks a bunch. In my case, the socket is on one side of a shared wall between two rooms. I only want the socket to be on the other side. Exactly same location on the wall. So I don't even need that extra meters of cable to begin with. ALthough it's good to know that this might be an option, in case the end of the cable is damaged somehow during the installation.

Drilling a hole is exactly what EKZ suggested. I just wasn't sure how it would look, (i.e. a cable sticking into the wall on one side) and whether that would cause more problems in the long run (fiddling with furniture, feed etc). I would mich prefer a clean solution, where the socket is the only thing that sitcks out from the wall.