Ian Stirling wrote:

Does it have to be cable warning marking tape?
I used yellow painted dexian (steel angle) 5cm over the conduit.

Reg. 522-06-03 of BS 7671 allows cable covers or marking tape. Cable
covers are usually pre-cast concrete things, not bits of old scrap iron.

Oh, hang on, you said conduit. The above is for a directly buried
cable. All it says for buried conduits is that they shall be "suitably
identified."

Also: "buried cables, conduits and ducts shall be at a sufficient depth
to avoid being damaged by any reasonably foreseeable disturbance of the
ground." This is usually considered to mean a minimum depth of 450 mm.

--
Andy