1836
1836: An Anglo-Spanish treaty was enacted that made it increasingly difficult for traders to utilize the Spanish flag for slaving purposes.
1836: An Anglo-Spanish treaty was enacted that made it increasingly difficult for traders to utilize the Spanish flag for slaving purposes. In response, many Spanish slave traders continued their operations by fraudulently adopting the flags of various other nations.
Source · p. 28
Eltis & Richardson, Atlas, 28