When the British Empire 'banned' the slave trade in its domains in West Africa in the 19th century, it organized various naval patrols along the West African coast as it attempted to intercept resistant slave ships that tried to break the law. Captured ships were sent to Freetown, Sierra Leone, where their human cargo were freed. As a result, Freetown became one of the first places to host a large diaspora Igbo population.
Fittingly, the first efforts to record the Igbo language began in Sierra Leone and were led by Bishop Ajayi Crowther, a linguist and former Yoruba slave and the first African Anglican bishop. After collecting vocabulary from former slaves of Igbo extraction living in Sierra Leone, in 1857 Bishop Crowther published the 'Ibo Primer', a work written in the Isuama dialect of Igbo (which he praised as the 'purest' and most intelligible dialect of the language). When his publication was employed in evangelical activities throughout Igbo land, it was wholly unsuccessful. His 'pure' Isuama Igbo was unintelligible to the natives. In one particular case, as a sermon was being preached to an audience, the presiding ruler of the community interrupted the orator midway with the complaint that they could not understand what he was saying. After many crushing failures, Bishop Ajayi completely abandoned his study of the Igbo language.