Colonial Nigeria was the area of West Africa that became the modern day Nigeria, during the time of British rule in the 19th and 20th centuries. British influence in the region began with the prohibition of slave trade to British subjects in 1807. The resulting collapse of African slave trade led to the decline and eventual collapse of the indigenous Edo Empire. Britain annexed Lagos in 1861 and established the Oil River Protectorate in 1884. British influence in the Niger area increased gradually over the 19th century, but Britain did not effectively occupy the area until 1885. Other European powers acknowledged Britain's power over the area in the 1885 Berlin Conference.