Whenever it appears that the occupant, or those under whom the occupant claims, entered into the possession of premises under a claim of title exclusive of any other right, founding such claim upon a written instrument as being a conveyance of the premises in question, or upon the decree or judgment of a competent court, and that there has been a continued occupation and possession of the premises included in such instrument, decree or judgment, or of some part of such premises, under such claim for twenty years, the premises so included must be deemed to have been held adversely.