Legacy record of 1820 slave departures from Luanda

A legacy record associated with this event states that 18,957 enslaved Africans departed Luanda in 1820, with a placeholder date of 1 January. No supplied passage confirms either the figure or the departure. What the sources do establish is that Luanda was the centre of the slave trade to Brazil from about 1550 to 1836, that Brazilian ships were the most numerous in its port, and that Angola was the principal source of slaves in the Atlantic trade during at least the 18th and 19th centuries. The 1820 record therefore sits within a documented trade but cannot itself be verified.