They marched in solemn procession through the streets of our towns and cities; religious leaders, foreign dignitaries, politicians and ordinary people compelled by conscience to mark the 200th anniversary of the abolition of slavery in Britain.

Yet it was no great cause for celebration. Because slavery, in all its insidious modern guises, still exists around the world today.

William Wilberforce merely began the process of freedom. Two centuries later, the massive task of completing that process - removing the yokes and chains from millions still enslaved - remains.

Debate continued over the depth of apology required for Britain's historic part in the practice. The Prime Minister beamed his regrets over a video link to Ghana, and a Scottish minister retraced the footsteps of a noted abolitionist.

Meanwhile, out of sight and earshot, millions of enslaved children were toiling in mines and mills, tilling soil, fighting wars and undergoing the most depraved kinds of abuse. What Wilberforce would have made of it can only be guessed at, but shocking new figures reveal that, 200 years after his Act of abolition, millions of children around the world - including Scotland - still live in bondage.

For 450 years, from the middle of the 15th century, millions of Africans were stolen away from their homes, packed like the commodities they were deemed to be into the dark, freezing holds of ships, many of them flying the British flag, and transported into servitude in the Americas.

The trade is still plied today. The charity Save the Children marked the 200th anniversary with a litany of the eight most prevalent forms of slavery that condemn children to live in appalling conditions, forced to work long hours for little or nothing in return and often subject to extreme harm, violence and rape.

They include child trafficking, prostitution, bonded labour, forced mine working, agricultural labour, enforced military service, forced child marriage and domestic slavery. It may be 2007, but still a little boy can be bought and sold for as little as £25.

Rhona Blackwood, spokeswoman for the charity, said yesterday that Nigeria was a common source of children brought into this country, but the traffic from China and Vietnam was also increasing.

Some have been found working in cannabis production houses, others in domestic and catering jobs or for sexual exploitation. Every year 1.2 million children and babies are trafficked and make $32bn (£16.5m) profit for the gangs involved.

"Trafficking is one of the worst forms of modern slavery. It is an abuse of children's rights and traumatises thousands of them every year," said Ms Blackwood.

Trafficked children come into this country on false papers or purporting to be asylum seekers, before being spirited off, either to be kept hidden or to merge into local ethnic communities.

"We want the Government to appoint guardians for separated children suspected of being trafficked into the UK," she said.

Events were held throughout the UK to mark the passing of William Wilberforce's bill to abolish the trade on which some of Britain's greatest cities - not least Glasgow - were built and on which its merchants grew wealthy.

The price was paid by some 12 million Africans who were shipped to the Americas, one million of whom died en route, the rest worked to death on the sugar and tobacco plantations.

The price is still being paid. At any one time 1.8 million children are being abused through prostution, child pornography and sex tourism - there are an estimated 5000 child prostitutes in the UK alone.

Millions are forced to work away their childhood in horrific conditions to pay off debt. They risk their lives in mines and quarries, and even farm work exposes them to pesticides, heavy machinery, machetes and axes.

Many of them are helping to grow the food we eat, dig up the minerals we use, and provide the kind services some of us would rather not talk about.

If they want someone to say sorry, they might have a long wait - it is 200 years since the events for which the Archbishop of York, Dr John Sentamu, was seeking a formal apology yesterday. We should be going "a bit further" than Tony Blair's expression of "deep sorrow and regret", he said.

"Britain is our community and this community was involved in a very, very terrible trade," said Dr Sentamu. "This is really the moment in which you say By the way, I think our forebears did a terrible, terrible thing'."

But Mr Blair - in a video message recorded for a major event in Ghana - stopped short of a full apology. He said the legislation had begun the process of ending "one of the most shameful enterprises in history".

It was an opportunity for Britain to express "our deep sorrow and regret for our nation's role in the slave trade and for the unbearable suffering, individually and collectively, it caused".

The UK's first black cabinet minister, Baroness Amos, who attended the ceremony, declared slavery to be "one of the most shameful and uncomfortable chapters in British history".

The Leader of the House of Lords - descended from slaves - was addressing the event at Ghana's Elmina Castle where thousands of Africans were held before being shipped abroad.

In Scotland, Communities Minister Rhona Brankin said slavery and its legacy still affected the modern world. "That is not just through criminal acts like people trafficking, but also through the iron grip that holds millions of people in poverty across the world," she said.

The minister took part in a Freedom Walk through Musselburgh organised by Action of Churches Together in Scotland to mark the anniversary of the act.

From a 21st-century perspective, the decision to abolish slavery looked like a simple choice between right and wrong that was easily made, Ms Brankin added. "But that would overlook the courage and conviction of many people who faced down the vested interests of those who sustained the evil trade in human lives.

"Many of those were Scots, and 200 years on from the passing of the Abolition of the Slave Trade Act, we should remember the vital contribution they made."

The walk, from the centre of Musselburgh to the Gardens at Inveresk Lodge, followed the steps taken by Robert Wedderburn, the son of James Wedderburn, who owned Inveresk Lodge, and Rosana, a slave maid on one of his Jamaican plantations. Robert came to Musselburgh in 1795 to visit his father. He did not receive a good welcome, and became a radical and anti-slavery activist.

Humanity in chains: 500 years of bondage
THEN:

- More than one million people are thought to have died in transit across the Atlantic through disease, malnutrition or violence.
- A male slave at the height of the trade could fetch £50.
- Caribbean slave owners were compensated to the tune of £20m when slavery was abolished.
- A further 9.4 to 14 million were taken from eastern Africa and enslaved in the Arab world.
- The last country to outlaw slavery was Mauritania, in 1981. The practice is said to persist but both candidates in the upcoming presidential election have promised to harden the law.



NOW:
- More people live in bondage now than were taken in the entire transatlantic slave trade.
- More than 218 million children aged between five and 17 are working as child labourers world-wide, with 8.4 million trapped in the very worst forms of illegal, dangerous and degrading tasks.
- According to Save the Children 1.2 million children are trafficked every year.
- An estimated 1.8 million are being sexually exploited for profit.
- More than 300,000 children, as young as seven, are serving as soldiers.