Agnes MacBean

Agnes MacBean was the driver of "Bertha", a private train owned by the Templar Rexford Kaylock. After the Frye twins eliminated Kaylock and took control of Whitechapel, they also became the new owners of the train, which was then turned into the Assassins's mobile headquarter and the new bosses of MacBean, who was unhappy under Kaylock rule.

Reference

 * Assassin's Creed: Syndicate Gameplay Walkthrough