Which european countries’ colonial possessions prevented the british from controlling the entire east coast of africa from the gulf of aden to the cape of good hope?

Italy and Portugal

Explanation:

The British Empire controlled modern-day Eritrea, Kenya, Tanzania and South Africa.

These colonies constituted the entire east coast of Africa from the Gulf of Aden to the Cape of Good Hope except for two territories: Somalia, which was controlled by Italy, and Mozambique, controlled by the Portuguese.