Why can't apache access files in /tmp?

[Chris Green]

I want to put some temporary html files in /tmp (well, a sub-directory
of /tmp) and view them using apache2.  I always get permission denied
and it seems as if apache2 refuses to access any files in /tmp.

I have a very simple apache2 set up with the root set to /srv with an
entry as follows:-

    <Directory /srv/>
            Options Indexes FollowSymLinks
            AllowOverride All
            Require all granted
    </Directory>

I add symlinks to /srv to get access to files around the system, it
works for every directory I've tried (even including such places as
/etc) but *not* for /tmp.  (I've removed all the odd symlinks again of
course!)

What's so special about /tmp?  I've searched for references to tmp in
the apache configuration but there's nothing there.

Can anyone suggest what the issue is?

Alternatively where can I put files that will get cleaned out
periodically (like files in /tmp at reboot)?

-- 
Chris Green