High Warden of the White Tower

From Tolkien Gateway

High Warden of the White Tower is a Gondorian title borne at least by Boromir, son of Denethor II. Boromir's brother Faramir told to Frodo Baggins and Samwise Gamgee in Ithilien that Boromir 'was the High Warden of the White Tower, and our Captain-General'.[1]

It is not known what responsibilities belonged to the office of the High Warden, or was it only a honorific title. No other bearers of the title are known. It is also possible that the title means the same as Captain of the White Tower, a title borne by Boromir,[2] and Faramir after him.[3]