 His sea career was summarised in evidence given to the House of Commons in 1789.The first venture in which King partnered with Anthony Calvert and William Camden was the voyage of the "Three Good Friends" to St Vincent via Cape Coast Castle in 1773 when he was joint master with Calvert.Ships of the firm made 77 voyages carrying slaves between the 1780s and the early 1800s and transported over 22,000 enslaved persons from West Africa, 65% of whom disembarked in Jamaica, 12% in the Guianas, 14% in other parts of the Caribbean and the remainder elsewhere; the firm's activities also included supplying British dockyards and overseas garrisons, whaling, transporting convicts, and trading in commodities from the East Indies.