wrote:
So the public should ignore any warning signs or advisory signs on
the
basis that they might be wrong. Should they also ignore announcements
over the pa on they basis that they may also be wrong.

yes. Especialy automatic announcements that seem to contradict
everything else. e.g. person on platform appologising for train being
diverted somewhere else at Earls Court and appologising for the
inconvenience being interupted by "District line services are oprating
normally".