21 June 1927
On 21 June 1927, Afrikaner nationalists  rebelled against plans to have a Union Jack (the British flag) in the centre of the national flag. The controversy followed the introduction of a bill to provide a national flag for the Union of South Africa in 1925 by D.F. Malan. The introduction of the bill came 15 years after the Union of South Africa was formed. The Boer community was still recovering fresh wounds from the defeat by British settlers in the South African War 1899-1902. Discussions about a new flag were taking place intermittently due to interruptions caused by such pressing issues as World War I and achieving Dominion Status within the British Empire. In 1925 the flag issue began to receive renewed attention. Different designs were suggested, but a compromise design was adopted, which saw the flag of the Republic of the Orange Free State hanging vertically in the centre of the white stripe of the Prinzenvlag. The Union Jack was spread horizontally towards the hoist from the centre and the flag of the Transvaal spread towards the fly. 

Boddy-Evans A. ‘This Day in African History: 21 June’, from About African History.com, 21 June, [online], Available at www.africanhistory.about.com (Accessed: 22 May 2012)|FOTW Flags Of The World website(2011), ‘South Africa 1928-1994’, 10 June, [online], available at www.crwflags.com(Accessed: 22 May 2012)