The Cruel Trade by Clifford Peacock

When a remote valley deep in East Africa is discovered and a handsome tribe, descended from the Queen of Sheba, is found living there The Sultan of Zanzibar is keen to establish his presence. Tippu Tip, the sultan's Machiavellian minister, orders a heavily armed expedition, led by the unwilling Captain Khalil, to seize the valley as a stepping-stone towards the sultan's ambition of ruling the whole of Africa. The Cruel Trade tells the story of a fascinating and brave expedition as it crosses the untamed savannah. A tale of betrayal and fear, but also courage and great love, this dramatic story gives an illuminating insight into a turning point in the long and bloody history of East African slavery.