The joint reflection has been posted on YouTube and is also accessible through the Archbishop of Canterbury's website. It was filmed at the site of the Slave Market in Zanzibar, now the island's Anglican Cathedral, during the recent Anglican Primates' Meeting. The Archbishops were shown two small preserved slave pits, where up to 175 men, women and children were held in appalling conditions, chained and in darkness, often without food and water. Sentamu spent some time at a memorial to the slaves which features some of the original chains used when the market was operating.

In the film, Williams says that the experience brought home the reality of the trade.

"You see there the fetters that were used for slaves. The fetters used to bring slaves in convoy, so that they could barely stand and walk. They were so closely shackled together," he said. "And to see some of the real, the actual shackles that were used until really very recently in this part of the world as part of the paraphernalia of the slave trade, it's a reminder that it really happened, it really happened not very long ago."

He said that the instinct to enslave is still very much present in the modern world. "It's as if slavery is a kind of compulsion for human societies. People go back again and again to treating people as objects, as possessions, and I don't think we can simply sit back and say 'it's a thing of the past and no more,'" he said. "All those modern forms of slavery -- economic slavery, debt slavery in effect, the slavery of sex trafficking -- these things are still with us."

Sentamu said that holding the original chains was a harrowing experience:

"I found the whole experience heart-rending ... When I went outside and actually saw those figures -- how slaves were tied together -- and touched the actual chains that were used, I was rendered absolutely speechless. I felt I was going back in history, but I was also in the present where slavery in some parts of the world still happens," he said. "Every person is made in the image and likeness of God, of great worth and of great value and to be treated with great dignity."

The Archbishops' reflection has been issued in the run up to the Church's Walk of Witness, to be held in London on March 24. The walk will be led by both Archbishops and will culminate in an act of public worship in Kennington Park, where the Archbishops will offer further reflections on the nature of the slave trade and its modern legacies.