Thanks to all who helped me solve this problem.
It eventually transpired that I had not one, but FOUR almost identical
docroot <Directory> directives in my configuration file(s) -- two
containing AllowOverride None; one containing AllowOverride All; and
one containing AllowOverride Authconfig. Obviously, I kept editing the
wrong one. :|
How they got there I have no idea. But I suspect a bit of 'mischievous'
editing somewhere along the line, by person or persons unknown, with the
aim of nullifying the authentication.
It actually took me longer to track this down than it should,
across the files concerned. Which begs the question: when is
Debian finally going to go towards a single httpd.conf file?
(Wouldn't stop this problem; but would help in tracking down multiple
and conflicting directives.)
Martin Wheeler - StarTEXT - Glastonbury - BA6 9PH - England
 firstname.lastname@example.org http://www.startext.co.uk/
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