To validate Portuguese claims, Serpa Pinto was appointed as Portuguese consul in Zanzibar in 1884 with the mission of exploring the region between Lake Nyasa and the coast from the Zambezi to the Ruvuma River and securing the allegiance of chiefs in that area. His expedition reached Lake Nyasa and the Shire Highlands but failed to make treaties of protection with 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. Its further ambition to control the Shire Highlands was given up in 1886 following protests from local missionaries that it could not police this area effectively.