Earth Security was a police force in operation on Earth by at least the year 2540. It was a global police force which tended to the security needs of the state headed by the civilian President of Earth. In practice, however, it may have been under the operational control of the military. (TV: Frontier in Space) More than 1600 years later, Earth Security still existed within the Earth Alliance. Alby Brook was a B-grade operative at the time of the Dalek invasion of Mutter's Spiral in 4162. His supervisor was Ernst Tanlee.(AUDIO: Invasion of the Daleks)