Tambo became deputy president of the ANC in 1958. He was chosen to represent the ANC overseas.
By 1963, Tambo was the most important ANC leader who remained free. Mandela became president in his president of the ANC in his prison cells; Tambo became acting as president.
Tambo's principal role was at the international spokesman for ANC. He was frequently in London and travelled widely to build international support for the ANC.