Harvey Parson

H. Parson was the headmaster at Coal Hill School in 1963 and, by extension, Ian and Barbara's boss. (TV: An Unearthly Child)

At some unknown point, the Imperial Daleks took control of him and used him as an undercover agent, implanting a thin device behind his ear. He was presumably killed as a security risk when the Imperial Daleks exterminated him, likely via his implant, so Mike Smith could not get information out of him. (TV: Remembrance of the Daleks)