Unity desktop environment - wrong (root!) user on elevation prompts

I'm using Ubuntu 16.04 desktop, however I'm having issues with the standard elevation prompts that appear when using the Unity desktop environment. Everything appears normal, I am logged in with my standard user account (named dan) and can successfully use this with the sudo command to run elevated commands.

However when asked to elevate when using the unity desktop environment it tells me to authenticate with the root user. I have not modified any settings to do with the root account (re-enabled or otherwise)

It probably goes without saying but as the root user does not have a password I caot authenticate myself with this account when prompted. I have tried my normal user password and this does not work.

Please see the attached screenshot

Thanks for your time.