You may be looking for Orderly (The Power of Three).

On Frontios, the Orderlies were an armed force tasked with keeping order. At the time that the Fifth Doctor, Turlough and Tegan visited, the Chief Orderly was Brazen. He had instituted several harsh measures designed to instil discipline in the colony — most notably the virtually on-sight killing of Retrogrades. (TV: Frontios)

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