[Mediawiki-l] Preventing user registration

[Nick Bell]

I hope you don't think this request is against the spirit of Wiki. I have
a mediaWiki site for doctors, and I need to prevent unauthorised access to
the pages. I've already prevented non-registered users from viewing or
editing pages - now I need to prevent all and sundry from registering and
hence becoming users. What is the easiest way of going about this?

Many thanks

Nick Bell