In April 1965, the rumour of a potential Kenyan coup was brought to British attention. This was a moment of raised tensions in the government of President Jomo Kenyatta, who secretly asked the British government for a military commitment to support his government if a coup was attempted by Kenyan Vice President Oginga Odinga. The British military responded by making an extensive military plan to intervene, code-named Operation Binnacle. They sent ships to Mombasa and put troops on alert. This article assesses these plans as a case study of the logic, and limits, of British military interventionism in the years after decolonization. It highlights the importance of studying plans, even when not carried out, and of taking seriously the attitudes and fears of contemporaries. Although a coup was highly unlikely, British reactions are revealing of their concerns about independent Kenya, including possible Soviet involvement. Operation Binnacle was a serious British response to the threat, as they saw it, which a coup would cause to their interests. These were extensive enough that the British government was prepared to intervene militarily, during a brief moment when military interventionism in Africa was still seriously considered as a possible policy choice.