On 16/04/2021 16:25, NY wrote:
....
This is the wiring https://goo.gl/maps/7TY9tJ2LNZfzEGE46 ...

The top three are the three phases. The bottom one is neutral and the
one between, which, if you look carefully is not insulated, is earth.

It was a common arrangement in some areas.

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Colin Bignell