The harsh climate, the British saw in West Africa as the “white man’s grave yard”. The excessive heat, mosquitoes, rainfall etc.
Britain was interested in trade after abolition of slave trade, all what the British were anxious about was legitimate trade with the natives as fruits, vegetables etc while British cloth, mirrors, rum etc interested in profit not annexation.
Britain was afraid of wars with the hostile inland tributes.
She tought Cameroon was not economically viable. Ie Britain did not want to increase the problems of her taxpayers et home.
Confidence in the treaties signed with King Douala and Bimbia since they thought that, they had signed with these people, any movement they can come and annex the territory.
The British felt that they had already enough territories like in gold coast, Nigeria, Gambia etc.
The differences between the foreign offices and the colonial office in London. The foreign favoured annexation while the colonial secretary lord Kimberly strongly opposed annexation.
Inadequate administrators. The british never had a lot admionistrtion who could control the territory.
The British feared the costly operations in administrating the territory and also trying to dismantle the middle man monopoly of trade enjoy by the people.
The British colonial problem France over Egypt and Sudan at the time made the reluctant to accept the require immediately.