It was proclaimed a British colony on 4 May 1843 after the British government had annexed the Boer Republic of Natalia , and on 31 May 1910 combined with three other colonies to form the Union of South Africa , as one of its provinces .
It was formed on 4 May 1843 after the British government had annexed the independent Boer Republic of Natalia . On 31 May 1910 , it unified with three other colonies to form the Union of South Africa .