14 August 1954
Walter Ulyate Sisulu attended a secret African National Congress (ANC) meeting in Durban. This meeting coincided with the "Congress of the People” which was held over the weekend 13 - 16 August 1954.
References

South African History Online‘The Freedom Charter is adopted in Kliptown’, [online], available at www.sahistory.org.za[Accessed: 06 July 2012]|O’Malley P. ‘1954’, from Nelson Mandela Centre of Memory and Dialogue, [online], available at www.nelsonmandela.org [Accessed: 06 July 2012]