Here’s a photograph from the June 17 1929 edition of the Toronto Daily Star of an African ruler who was visiting London.

Khalifa bin Harub of Zanzibar (1879-1960) ruled Zanzibar, then a British protectorate, from 1911 until his death. He doesn’t seem to have done anything particularly startling.
The sultanate of Zanzibar only lasted for three years after this sultan’s passing. In 1963, Britain granted independence to Zanzibar, which was intended to become a constitutional monarchy under the rule of the sultan. One month later, a revolution forced the last sultan of Zanzibar into exile. Later in 1964, Zanzibar and Tanganyika united to form the country of Tanzania.