On Monday, 12 October 2020 10:13:39 UTC+1, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

Saw electricity supply to a new housing estate being laid the other week. Three lots of "twisted three" in a trench - with plenty of very hefty sealed junctions. All outer layers were red. Didn't see the actual covering process but suspect a bit of gravel then some concrete and asphalt.