Ooli

 was posing as a police officer in Northern England. She didn't like Alistair Gordon Lethbridge-Stewart getting involved in her investigation. She hypnotised the Brigadier to stop him bringing in more troops and she tried to do the same to Al Sinclair. She didn't want people knowing of her sacred mission on Earth and disintegrated people who learnt of it. She was on Earth to stop the Grestrenor by Galactic Ecology Enforcement Council. She tried to convince the Brigadier and the Third Doctor that they were on the right side, but she wanted to destroy humanity. (AUDIO: The Annihilators)