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 relation to time - that the act of using a clock to measure time changed time - and Orthopositronium coated mirrors to achieve time travel. This set-up worked first after the effects of the Daleks' Temporal Extinction Device, then in the presence of a source of chronons. He was killed by the Daleks. (BFA: The Time of the Daleks)