Captain Everard Wibert is one of the Captains of the City Watch.  There are nearly a dozen Watch officers with that title, each with a jurisdictions that roughly corresponds to one of the Districts in the city.  

Captain Wibert is a Watch Captain "at large", and can be seen in nearly any district.  He is a close confidant of the Commissar, and is generally considered to be an honest and trustworthy, which cannot be said of all of the Watch Captains.