Christian McArdle wrote:

So, are all those buildings with steel armour as the only earth
unsafe after decades?

Potentially. It is one of the many reasons for the move towards TN-C-S
earthing, where the earth is carried by the neutral conductor.

Uh, that's TN-C and isn't allowed in consumers' installations.

Rusting/corrosion of steel armour wires is not a problem, galvanizing
protects well.

--
Andy