 Mathews retired from the Royal Navy in 1881 and was appointed Brigadier @-@ General of Zanzibar . There followed more expeditions to the African mainland , including a failed attempt to stop German expansion in East Africa . In October 1891 Mathews was appointed First Minister to the Zanzibar government , a position in which he was " <unk> by the sultan " . During this time Mathews was a keen abolitionist and promoted this cause to the Sultans he worked with . This resulted in the prohibiting of the slave trade in Zanzibar 's dominions in 1890 and the abolition of slavery in 1897 . Mathews was appointed the British Consul @-@ General for East Africa in 1891 but declined to take up the position , remaining in Zanzibar instead . Mathews and his troops also played a key role in the ending of the Anglo @-@ Zanzibar War of 1896 which erupted out of an attempt to bypass the requirement that new Sultans must be <unk> by the British consul . During his time as first minister Mathews continued to be involved with the military and was part of two large campaigns , one to Witu and another to Mwele . 
