On 23 May, 10:23, Andrew wrote:
On 22 May, 22:33, fred wrote:

Are these wall lights? Are you running the wiring in the wall or in the ceiling
part of the stairs? If you are running the wiring in the walls then you have
150mm in the corner between wall and ceiling as a permitted route or if
you are running the wiring in the plane of the (slanted) ceiling and not
deviating from side to then it isn't diagonal at all.

There are small 'step' lights, one every three steps that are recessed
into the wall about six inches above the step in question. So a long
way from the ceiling which in any case is horizontal for the length of
the stairs. Switches are already in place and there is a junction box
under the landing floor for connecting into. The wiring will go from
the floor vertically to the first light then diagonally connecting all
the others. Or at least, that is the plan.

Andrew

Rather, diagonal is the shortest route. Staying in the regs is easy,
since you can go horizontal or vertical from a fitting, then why not
go up 3 steps worth of height and then across to the light. No need to
go diagonal and no need to protect. Basically go along the other 2
legs of a right angle triangle.
There is no need to go all the way to the ceiling, across and down
again if you think about it.
Interested to know if anyone thinks this would be a problem, as far as
I can tell it would be entirely compliant.

Fash