British involvement with the Nigerian coast was from the days of the slave trade in the Seventeenth Century. British traders would bring simple manufactured goods and exchange them for slaves from the interior. The British found the climate and diseases too harsh. They were reluctant to enter the interior or leave the security of their ships or factories. The coast provided some relief from the oppressive heat and reduced, but did not eliminate, the chances of catching nasty diseases. It wasn't called the 'White Man's Grave' for nothing. The lure of the fabulous opportunities and profits of the slave trade was enough for many Europeans to risk the hostile environment.
By the end of the 18th century British enterprise had almost entirely displaced that of other nations on the Niger coast. But the principal trade of all Europeans was still in slaves. They did not however claim any formal ownership or control. Coastal tribes were populous and powerful. They also benefitted from the slave trade and often used their resources to invest in sophisticated European weapons. The British tended to confine their factories and forts to the mouths of the large river systems that emptied into the Bights of Benin and Biafra.
After the British banned the slave trade in the early Nineteenth Century, they switched their trade to palm oil. In fact, this trade became so important that the area became known as the Oil Rivers. Oils were needed as lubricants for the new industrial engines back in Europe and it was also used to make soap.
The Royal Navy actually increased their presence in the area as they attempted to suppress the continued slave trade. Britain's abolition had been a unilateral one, other European nations continued it. The rivers and islands provided excellent collection and hiding places for slave traders. The Royal Navy occupied the nearby island of Fernando Po to use as a base. However, the Spanish claimed the island back in 1855. The Royal Navy therefore switched its base of operation to Lagos island in 1861. The Royal Navy actually dedicated a sixth of its entire surface fleet as this 'preventative squadron'. This squadron's powers were limited until all the major countries participating in the trade (except the United States) ceded Rights of Search to the Royal Navy in the 1830s. This anti-slavery enterprise had a momentum of its own. More and more consuls and political agents became actively involved in the area. Their intelligence gathering revealed more than just details of slave trading, it also revealed detailed economic information which was to benefit British commercial interests. It also formalised relationships with African leaders as the British would force them to enter anti-slaving agreements.
The British had been content to keep their presence limited to the coast and the mouths of the rivers. However, in the 1880s the French made it clear tht they were keen on increasing their influence in the area. They had already sent expeditions from West Africa to hem in the colonies of Gold Coast and Sierra Leone. However, the British were going to try and stop the same thing happening in the case of Southern Nigeria. George Goldie would be the prime mover of this initiative. He was a businessman with considerable interests in the area. He used his United African Company to buy out and amalgamate British interests in the area. In 1884, he also could take advantage of French reverses in the Far East to buy out worried French investors in West Africa.
The arrival of the Germans in the area was to be a further spur to action. They had annexed Togoland and Cameroon and made it clear that they were ambitious for more territories. It was at this point that the major European nations called together a confernce in Berlin to sort out the contrasting and competing claims. In fact, the Germans were playing something of a double game. Bismarck was little interested in colonial adventures except that it added leverage to his European designs. Although it should be said that the Kaiser was much more in favour of a 'place in the sun'. Britain basically had to say that it claimed the protectorates of the Northern and Southern Nigerias or risked losing them to the French or the Germans.
Northern and Southern Southern Nigeria were united in 1914.