Roman legions encountered the strongholds of the Castle Rock and Arthur's Seat, held by a tribe of ancient Britons known as the Votadini.
Castle Rock and Arthur's Seat used to belong to the Votadini. 
mnli hypothesis: Castle Rock and Arthur's Seat used to belong to the Votadini.  premise: Roman legions encountered the strongholds of the Castle Rock and Arthur's Seat, held by a tribe of ancient Britons known as the Votadini.