Milton

Milton was a terrorist who was an agent of an unknown operation. She forced Toshiko Sato to make her a Sonic Modulator in exchange for her mother. (TW: Fragments) The exact reason she wanted/needed the Sonic Modulator is currently unknown. The fact that The Doctor once partly worked with UNIT, who had the blueprints, may mean that Milton is possibly aware of The Doctor and his Sonic Screwdriver. This can further be supported by the fact that orginasations such as UNIT keep secrets and are aware of The Dcotor among other things that are mostly hidden from the general public.