@Tim turns out I’m subclassing SecurityAdmin (couldn’t get desired functionality to work as an extension). Commenting out the sub class removes the duplication (but also of course the added functionality). Is there a way to prevent items automatically being added to CMS Menu? Or to override the default name?
The subclass is intended to extend SecurityAdmin so that custom messages can be sent out to selected members as per Sending email to a subset of members (my preference would be to use an extension instead, but wasn’t able to get it to work - I have many other extensions working on my site, so maybe SecurityAdmin can’t be extended or I’m missing something???)