The EIC’s mixed-cargo slave trade was further distinctive in that not all of the slaves were purchased by the company; many were born into slavery at the company’s holdings and then moved to another fort. When EIC directors in London received a request for slaves from one of their agents, they would first look to the slaves they already owned and attempt to transfer them. The EIC’s slave trade strategy relied heavily on the transfer of slaves between holdings. According to the estimations of Richard Allen, as many as one-third of the slaves aboard EIC ships were transfers—a sizeable proportion given that transfer requests were consistently smaller than purchase requests. The company authorized at least 77 transfer voyages involving at least 1,040 slaves between 1639 and 1787.