Accra, Ghana (CNN)Britain's Prince Charles spoke out strongly against modern slavery at a conference in Ghana, once the embarkation point for many Africans traded as slaves.
Prince Charles condemns modern slave trade
Charles, on the second leg of a West African tour, said Monday it was unimaginable the suffering the trans-Atlantic slave trade caused and that it left an "indelible stain on the history of our world."
British traders were among the largest participants in the Atlantic slave trade in which up to 12 million Africans were estimated to have been sold into slavery. Britain abolished the trans-Atlantic slave trade in 1807.
"Britain can be proud that it later led the way in the abolition of this shameful trade," said Charles, the heir apparent to the British throne. "We have a shared responsibility to ensure that the abject horror of slavery is never forgotten, that we abhor the existence of modern slavery."
The Prince of Wales and his wife, Camilla, the Duchess of Cornwall, visited Osu Castle, a one-time slave fort in Accra, on the Atlantic coast's Gulf of Guinea.
Built in 1661, the castle was a principal holding cell for enslaved Africans during the trans-Atlantic slave trade. It also was the headquarters for the British colonial government.
The duchess also stopped by the Ghana International School to highlight the Commonwealth Essay Competition prize, an international writing competition that the Royal Commonwealth Society has managed since 1883.