It's not an activity you'd normally associate with a relative of the Queen but Viscount David Lascelles is busy learning black street culture.

The 56-year-old great-grandson of King George V, heir apparent to the Earldom of Harewood, and film producer, is being given impromptu tuition by Leeds' black community, as he prepares to produce Carnival Messiah.

The exuberant work, which combines the excitement and colour of carnival with the inspirational melodies of Handel's Messiah, is being staged at Harewood to mark the bicentenary of the Abolition of the Slave Trade.

Chapeltown resident Sheila Haworth revealed that they are passing on a few hints to the Viscount, who is currently 40th in line to the throne - and he cheerfully admits it's true.

Sheila, who is carnival's community liaison officer, said: "David has been teaching us. But he has been learning from us as well - things like street culture."

He laughingly acknowledges his educational progress, to the amused approval of his new teachers.

"I know a little bit of street culture - I'm sure I have learnt some new words. I am learning the concept of liming - or hanging out," he says.

It is the sort of jokey banter which seems perfectly normal today.

But it would have been a very different story two and a half centuries ago when members of the Lascelles family were heavily involved in the slave trade.

The magnificent house that dominates Harewood today was built with the fortunes which were made in large part on the back of slavery.

The family's connection with Barbados began in the 17th Century when Edward Lascelles and his son, Daniel, lived in Bridgetown.

It was Daniel's three sons - George, Henry and Edward - who went on to found the family fortune, working as sugar merchants, money lenders, slave traders, plantation owners, suppliers to the Navy and customs collectors.

In the four years between 1713 and 1717 Henry had a share in 21 slave ships and was partly responsible for the trading of thousands of human beings.

By 1787 the family had a financial involvement in 47 plantations across the whole of the West Indies.

Evidently astute businessmen they gained immense wealth, and in 1739 Henry Lascelles bought the Harewood and Gawthorpe estates for £68,828.

When Henry committed suicide in 1753 he left a vast fortune estimated to be worth more than £28m in modern terms.

His eldest son, Edwin, commissioned the magnificent stately home at Harewood which was completed in 1771. Born in Barbados, he spent his life as an absentee landlord - although he still managed to write a book Instructions for the Treatment of Negroes' in 1785.

Encompassing the sheer, awful brutality of the slave trade, not to mention allegations of corruption against Henry and Edward, it is a less than salubrious history by modern standards.

But the Lascelles family were not unusual in their involvement in the human trafficking. Countless people including merchants and members of the aristocracy built fortunes on the suffering of Africans and even the Church of England was in on the act.

David Lascelles, who has opened up the family's archives to the public, stressed that the profits from the slave trade permeated the whole fabric of life in Britain.

"Actually the country's economy was pretty much based on it," he said. "It was at the core of everything."

But, he said, despite its importance to the economy of the country there a great deal of ignorance among the general population about what was actually happening - followed by moral revulsion when the facts became known.

By the 1780s the tide was turning, and the Society for the Abolition of the Slave Trade was formed. By 1807 the Bill for the abolition of the slave trade was passed When Henry Lascelles, later 2nd Earl of Harewood, stood against Wilberforce and Lord Milton in the 1807 election his opponents used his connection with slavery against him.

Electioneering pamphlets from the time carry the slogan: "No Slave dealing Lord. No Yorkshire votes purchased with African Blood. No Lascelles, no never! Milton for Ever.' But the Lascelles camp had their own take on the argument.

"No Slave Trade! Who voted against the abolition of the Slave Trade? Earl Fitzwilliam, The Father of Lord Milton deny it who can? Who did not vote against the Abolition, the Hon H Lascelles, who always prefers his conscience to his Interest."

Whilst it was accepted that Wilberforce would be voted in, the other two fought a dirty campaign, and Lascelles lost by a narrow margin.

The abolition did not come into effect until 1808, and then had a limited impact as the Royal Navy could not police all ships crossing the Atlantic.

Slavery ceased finally in 1833 when the Slavery Abolition Act was passed. Three years later Henry Lascelles received £26,309 as compensation from the British Government for the loss of his slaves after emancipation.

Now two centuries later the Lascelles must surely be one of the most ethnically diverse branches of the Royal Family - with members who have married into the family in recent years including a Native American and a black African princess.

And today David describes the business which helped build his family's wealth as brutal and dehumanising trade'.

He added: "Much of Britain's wealth in the 18th century, when the trade was at its height, was built on the hard labour of the slaves in the sugar plantations of the West Indies and the Lascelles family made as much money out of it as anybody. Henry Lascelles - banker, owner of ships, slave and plantations, Controller of Customs and exclusive provider of supplies to the Royal Navy in Barbados - bought land in Yorkshire with the fortune he amassed.

"His son, Edwin, built Harewood House there and commissioned the artist, craftsmen and designers to fill it with beautiful things.

"Today, more than 250 years after Henry Lascelles made his fortune, Harewood House is one of Yorkshire's leading visitor attractions, with around 250,000 visitors each year. Since 1986 it has been an educational, charitable trust, run for the public benefit with an award winning education department and a vibrant contemporary art programme.

"Nevertheless, some in Leeds West Indian community and beyond still see Harewood as a symbol of that cruel tragic time.

"So it's not really surprising that people ask: "What are you going to do at Harewood for the bi-centenary?

"I was clear in my own mind what we should not do: indulge a sense of guilt about a past that - however appalling - can never, ever be changed. Instead, we intend to mark the bi-centenary in a range of ways."

Those ways include the staging of Carnival Messiah which is seen as a way of bringing communities and cultures together, and which its supporters say has already changed lives.

David said: "There is always this big debate about whether people should apologise. At best it is a symbolic act - and it doesn't really change anything."

But he believes projects such as the carnival messiah can bring about real change today.

He also believes it is import to acknowledge the past and make information available, and Harewood has produced its own booklet to commemorate the bi-centenary and the 1807 election.

In addition it is making publicly available information contained in the Lascelles Barbados Papers which have been re-discovered in recent years after sitting in unopened boxes at Harewood and at the archives at Sheepscar.

"Some of it was literally found in a box in a cupboard not that long ago. Everything is pretty well catalogued here now but still things like that do turn up."

The papers give a fascinating insight into the family's day to day business dealings.

He said: "I am not a historian - but the details of these stories are always to me more interesting than the broad strokes.

"The way they operated as businessmen was extremely interesting and very much of its time.

Henry Lascelles, who was originally a banker, ended up owning a large number of plantations by default, and is described by David as a sophisticated businessman'.

But whatever his personal views about the trading of human being they are not recorded in the papers.

"They are business document, and I have no idea whether the family were particularly cruel or kind. I just don't know."

The importance of education is reiterated by Sheila Haworth, community liaison officer for Carnival Messiah, who says many black people have themselves been unaware of their black British heritage. And she stressed the importance of different ethnic groups working together.

"David will learn a lot from our culture and we will learn a lot from his culture.

"I used to come to Harewood when I was a kid, and to me it was like they were different to us - but they are not different. David has the same sort of morals and ideas as me."