He was the son of Thomas Cave, a Liberal Member of Parliament, and one of his brothers was George Cave who would become a Conservative Home Secretary and a Viscount. Basil Cave worked for the Foreign Office as a civil servant and was appointed Vice-Consul of British East Africa in 1891. In 1893 he was placed in command of a number of soldiers during civil disorder on Zanzibar and in 1895 was appointed Consul to the country. The Consul-General, AH Hardinge being away, Cave was responsible for starting the Anglo-Zanzibar War in 1896. He issued an ultimatum to Khalid bin Barghash who had seized the throne on the death of Sultan Hamad. The resulting 38-minute war, the shortest in history, ended with victory for Britain and the installation of their chosen Sultan, Hamoud bin Mohammed.