Ruth Horwitz

 was a physicist who worked at St Ursula's College in 1939 and was very work conscious. She was Jewish and received anti-Semitic pen letters for three months, beginning in June 1939. She showed the letters to Peri Brown. Someone tried to kill her and her room was ransacked. The Sixth Doctor asked her to tell the truth: she owned an alien eye that turned things invisible, but it was unstable so she couldn't use it for her desired result, to conceal whole armies to help invasions. (AUDIO: An Eye For Murder)