Wiring Regs do not allow cables to run diagonally unless protected which seems eminently sensible since it is not the most obvious route.
I now have to wire a series of lights that illuminate the stairs and thus by definition run in a diagonal fashion. The most obvious wiring is diagonally between each light, any other route would, I think, be counter-intuitive. Would metal channelling be acceptable as mechanical protection in this instance? It is likely to be a 12v supply.
Andrew