[1] Turnbull wrote to Lord Palmerston, the British foreign secretary at the time, arguing that slavery was "the greatest practical evil that ever afflicted mankind.

"[2] Turnbull had spent the latter part of 1838 and early 1839 travelling in Cuba, where slavery remained legal.

In 1840, he produced his best-known work, Travels in the West: Cuba; with Notices of Porto Rico and the Slave Trade.

In 1844, the so-called Year of the Lash in Cuban history, there was apparently an aborted slave revolt known as the Conspiración de La Escalera.

[3] After revelations about the revolt, thousands of enslaved and free Afro-Cubans were executed, imprisoned, or banished from the island.