Division Three was a fictional British government agency. It first appeared in the 2011 Jeffery Deaver novel, Carte Blanche. It was loosely affiliated with the Security Service (also known as MI5); however, unlike MI5, Division Three had more than broad investigation and surveillance powers. Division Three also had arrest authority and tactical officers. It engaged in tactical and operational missions within the UK's borders to investigate and neutralise threats. Division Three was based in Thames House.