To validate Portuguese claims, Serpa Pinto was appointed as its consul in Zanzibar in 1884 and given the mission of exploring the region between Lake Nyasa and the coast from the Zambezi to the Rovuma River and securing the allegiance of the chiefs in that area. His expedition reached Lake Nyasa and the Shire Highlands but failed to make any treaties of protection with the chiefs in territories west of the lake. At the northwest end of Lake Nyasa around Karonga, the African Lakes Company made, or claimed to have made, treaties with local chiefs between 1884 and 1886. Its ambition was to become a chartered company and control the route from the lake along the Shire River.