Marchers wearing yokes and chains set off Thursday on a 250-mile trek to London to mark the 200th anniversary of the abolition of the British slave trade.

The northeastern port city of Hull was the home of William Wilberforce, who led a 20-year campaign in Parliament to abolish the trade — a goal achieved on March 25, 1807.

However, it was another 26 years before Britain banned slavery in its possessions, mainly in the Caribbean.

One of the marchers, Andrew Winter, said Britain's history as one of Europe's leading slave-trading nations is "a scar on our nation that we have not dealt with."

"Foremost we want to bring about an apology from Britain and Europe and the slave trading nations, saying sorry for our involvement in that," Winter said.

William Wilberforce, a great-great-great-grandson of the parliamentarian, and Kate Davson, a great-great-great-granddaughter, joined the group as it left Holy Trinity Church in Hull.

The walk is the final stage of the seven-year Lifeline Expedition.

The group plans to be in London by March 24 to join a Walk of Witness led by the leaders of the Church of England, Archbishop of Canterbury Rowan Williams and Archbishop of York John Sentamu.