Actually, come to think of it, there is a possible failure mode in a
TN-S system where the earth disappears but L&N are still live. That
could be quite dangerous too, if a fault develops in your
installation...

Indeed. It is more dangerous than the PME case, as with PME you would have a
power cut that causes the fault to be fixed. If you lost only the earth but
not the neutral, you could continue in that state for some time without
anyone realising that a fault has occured.

Christian.