 On 5 November 1842 Cumming was appointed to the newly built 16 @-@ gun sloop HMS Frolic , under the command of William Alexander Willis . Frolic was posted to South America and on 6 September 1843 Cumming was cruising off Santos , São Paulo , in command of the ship 's pinnace , when he encountered the large brigantine Portuguese slaver Vincedora in company with two other slaving vessels . The British slave trade had been outlawed by the Slave Trade Act 1807 and the Royal Navy viewed all slavers as pirates , liable to be arrested and their ships confiscated . Cumming positioned the pinnace to cut off the Vincedora 's retreat but the brigantine made to ram the boat . At the last moment , perhaps wary of intentionally killing a Royal Navy officer and his men , the Vincedora changed course . Shortly afterwards Cumming was able to shoot the brigantine 's captain . 
