Spur through a dividing wall?

We have a double socket on the living room side of a dividing wall to the hall. Is it allowable to install a spur through the wall to put a single socket on the other side directly opposite the double? The wall is two bricks thick plus plaster, boxes are 25mm.

Seems daft to bury cable to the ceiling on both sides but I don't know what the regs say.

Thanks.

back to back is fine..
might want to go easy with the chisel and the drill though so you don't knock the old box out of the wall or drill into it from the other side..

Thanks ColJack. Living room box is also new ie. not yet fitted, so no danger of damage.

I first thought the single could just be on the main ring but I think a spur will be easier to wire through the back of the double box,as it were.