27 May 1963
Jomo Kenyatta was elected Kenya’s first Prime Minister, in 1963, following that country’s independence from Britain. In 1964 he became the first President of the Republic of Kenya. A few years earlier, Kenyatta had been sentenced to hard labour and was restricted following his arrest in 1952 related to allegations of his complicity in the Mau Mau rebellion. He was released on 14 August 1961. 
References

Page E.M. (2003), Colonialism: An International, Social, Cultural and Political Encyclopaedia, p.313| Kisangani F.E. & Bobb S.F. (2010), Historical Dictionary of the Republic of Congo, (Scarecrow Press), p.475