Overton

 was a MI5 operative who was tasked to oversee Hassan Al-Nadyr's visit. She later chastised Hassan after he didn't allow her staff to join his. She asked him about the assassination attempt. She later wanted to search Toby Kinsella's office. She later questioned Ian Gilmore, Rachel Jensen and Allison Williams. (AUDIO: Who Killed Toby Kinsella?) She got information about Countermeasures and thought they wanted to kill Hassan and the Prime Minister. She later tried to arrest the countermeasures team but they had diplomatic immunity. (The Dead Don't Rise'')