Osric (The Time of the Daleks)

 was a scientist in charge of Mariah Learman's time travel experiments. He used Heisenberg's Uncertainty Principle in the relation to time, that the act of using a clock to measure time changes time, and Orthopositronium coated mirrors to achieve time travel. This set up worked firstly after the effects of the Daleks' Temporal Extinction Device, then in the presence of a source of chronons. He was ultimately killed by the Daleks. (BFA: The Time of the Daleks)