In the past year or so the only account registrations at the Wiki have been from spammers and vandals. My chief activity on the Wiki over the past few months has been blocking these accounts and deleting their contributions.
Today I have attempted to turn off account registration except by sysops. It appears to have worked.
If there should happen to be any genuine registree in the future please direct them to contact me via the forum pm system.
I will be emailing offroadgeek to let him know what I've tried to do.
I've clearly labelled the changes to LocalSettings.php so other sysops can turn registration back on if necessary.