3 May 1781
Piet Retief was one of the leaders of the Great Trek that introduced Afrikaner settlement to the interior. Prior to their departure from Cape Town he wrote a manifesto to the Grahamstown Journal bitterly complaining about the abolishing of slavery and the free movement of freed slaves in the Cape. Also added to their complaints was the British 'Anglicization' of the Cape.
References

Sources: Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau.