Richard wrote:
I'm going to run power to a pair of lights in the pillars either side of
my gate when the drive is relaid.
Having miles of 2.5 T+E dated prior to 2005 can I use this provided it
is (a) buried in a sand lined trench of suitable depth below the drive,

No. PVC T&E is not suitable for direct burial

(b) marked with that yellow warning tape and

This is usual for any type of cable, but does not change the fact that
PVC T&E is not suitable for direct burial

(c) in some sort of protective tube?

Yes, but ...

I had 1" overflow pipe or 22mm polypipe in mind for the protection. Is
that suitable/acceptible?

No, because it isn't manufactured to the relevant British Standards for
buried-conduit-for-electric-cable, so wouldn't comply to the IEE Regs
which require things to be made to appliccable British Standards. If for
no other reason, it's probably not the right colour for a buried cable duct.

Just buy some armoured cable and do the job properly. We won't tell
anyone, honest. (And if the job is done in pre-2005 T&E inside the house
and the junction to armoured is concealed-but-accessible I don't think
anyone will notice.)

Owain