premise: Thameslink and Great Northern are the brand names used by the Govia Thameslink Railway train operating company on the Thameslink and Great Northern routes of the Thameslink, Southern and Great Northern franchise, previously operated by First Capital Connect.
hypothesis: Thameslink and Great Northern are the brand names used by the Govia Thameslink Railway train operating company on the Thameslink and Great Northern routes of the Southern and Great Northern franchises, only.
reason: It also operates as part of the Thameslink franchise.