The Archbishops of Canterbury and York have led a procession through London to mark the 200th anniversary of Britain's abolition of the slave trade.
Campaigners who walked from Hull had their chains removed
Dr Rowan Williams and Dr John Sentamu were joined by foreign dignitaries and leaders of other churches for the Walk of Witness.
Dr Williams said it was a way Anglicans could try to heal "historic injustices inflicted in the name of the Church".
Last year the Church of England made a formal apology for its role in slavery.
The Church held slaves on plantations in the Caribbean.
An amendment "recognising the damage done" to those enslaved was backed overwhelmingly by the General Synod in February 2006.
The bicentenary of the 1807 act that banned the slave trade in the British Empire falls on Sunday.
The Church said the archbishops wanted people to reflect on the horrors of the transatlantic slave trade and use the anniversary to tackle the impact of its legacies, including "examples of human trafficking and oppression across the globe".
Dr Williams said slavery had contributed to the downward spiral of nations trapped in poverty.
"The intention of today is not only to renew that act of repentance, not just an apology but repentance, acknowledgement that we were part of this terrible history, but also to wake people up to where we are now, the fact there still are problems.
"It's an opportunity to involve people whose ancestors were involved in this, who are still feeling the effects of it, and so bring to light some of what it meant, some of what it cost."
Yokes and chains
The walk went from Whitehall, past the Houses of Parliament, and across Lambeth Bridge to Kennington Park, where there was a service of commemoration.
In the procession was a group who walked 250 miles from Hull - the parliamentary seat of the abolitionist MP William Wilberforce - in yokes and chains.
At Lambeth Pier, the archbishops led prayers while holding a wreath marked 2,704 - the number of ships that left London destined to carry slaves during the transatlantic slave trade.
The Archbishop of the West Indies, Drexel Gomez, who symbolically released the Hull walkers, told BBC Radio 4's Today programme he believes an apology is in order.
He said: "We have to acknowledge our past if we are to build a future, and such acknowledgement will pay attention to the degradation and the inhumane ways in which persons have acted in the past, which forms part of our history and heritage whether we like it or not.
"By acknowledging what's happened in the past we own up to what has gone wrong and chart a way forward for us to avoid such acts for the future."
However, Christopher Madres-Smedley, a descendant of plantation owner John Pinney, says he does not propose to apologise.
He said: "I feel very strongly that an apology is a great human act, and a very good act, but you apologise for what you have done.
"Slavery stopped 200 years ago, that's quite a lot before I was born, I am therefore in no position to apologise."
It has been estimated that between 10 and 25 million Africans were transported across the Atlantic during the slave trade.
The wreath will be transported by boat towards the docks before being taken to Westminster Abbey for Tuesday's national service to mark the bicentenary.