RubberBiker wrote:
Simple explanation - chap had run out of correct wiring, had to get
the job done - used what he had in the van. Didn't even bother about
earths.

Sometime later, wiring inspection failed, someone else adds in earths.
There was a period, 70s I think when cable was in short supply and
various strange cable types got used. I removed quite a lot of copper
'plated' aluminium t&e when re-building my house in the early 80s.

Bob