Having just had a new electricity supply laid on, I was kind of
surprised to see that the incoming cable has only one core; ie the
earth and neutral are combined. Having just googled a bit I can see
that this is perfectly normal practice, but what I don't understand is
how this configuration translates to my domestic supply. Evidently
neutral and earth are at the same potential, right? So how does
earthing work within my house? Sounds daft to be asking, but what is
the advantage of earthing the circuits in the house? ie, why do we
have a separate earth within the house but not from beyond the
consumer unit?

Would be grateful for some clarification!

Thanks
David