This article provides, for the first time, a detailed and authentic account of the genesis and planning of the Somali Expedition, derived from previously unresearched documents in the Oriental and India Office Collections of the British Library, and supplemented by material from the archives of the Royal Geographical Society. The author has sought to give the subject a wider historical perspective than that provided by Burton, by including details from the works of earlier travellers in the north-east region of Africa such as James Bruce, Lord Valentia, and Henry Salt, which, to a greater or lesser degree, have a bearing on Somalia. He has also touched on the ‘Eastern Question’, especially with regard to Muhammed Ali's territorial ambitions in Arabia, which was an important factor in the British decision to annex Aden in 1839, leading inevitably to the development of an important relationship, both commercial and strategic, with the Somali coast across the Gulf.