 On his return, he published a book entitled "An Alliance to Raid for Slaves".It is estimated that Hawkins transported 1,500 enslaved Africans across the Atlantic during his four voyages of the 1560s, before stopping in 1568 after a battle with the Spanish in which he lost five of his seven ships.The English involvement in the Atlantic slave trade only resumed in the 1640s after the country acquired an American colony (Virginia).