The astonishing story of how a Bradford woman traced her roots to mid-18th-century Jamaica is being told in an exhibition to mark the 200th anniversary of the abolition of the slave trade.

Jennifer Thornton's great-great-great-great grandfather was John Yorke, born a slave and freed when he saved a gamekeeper from a moor fire on an estate in North Yorkshire.

For his bravery John was given a cottage in which to live and bring up his family.

His amazing story from Jamaican plantation as a small boy and marriage to a Yorkshire lass, Hannah Barker, in 1799, took years of painstaking research by Mrs Thornton, who lives in Clayton and works for Bradford District Care Trust, and her family.

It so impressed bosses at the Yorkshire Dales National Park that it has been featured in their exhibition Hidden History of the Dales, People and Places'.

Mrs Thornton has visited the site of the Fish River plantation near Montego Bay from where John was brought to England by the owner's daughter Elizabeth Campbell.

She married wealthy widower John Yorke, of Richmond, and it was then that Mrs Thornton believes he was given his new master's name, John Yorke.

But by 1772, John had moved into the ownership of John Hutton of nearby Marske Hall. That year, all black slaves in England were freed but it would be another 35 years before the abolition act came into being.

John's life improved when he saved the gamekeeper's life and was given the cottage. The family he raised there has 130 descendants, but only 14 in the male line.

Mrs Thornton is descended from John's prizefighting son William, born in Marske in 1803. His son George moved from North Yorkshire to Bradford to work at Bolling Iron Works. He died in 1910.

Mrs Thornton said: "When I found out I was related to a slave I was amazed. But when I learned about John and his life and of his family I was very proud.

"I think he too would be proud of what has happened to his family over the years.

"I feel quite humble that I have come from stock which suffered untold hardship.

"To think that, if not John, then one of my ancestors had to come across from Africa to Jamaica on a slave ship and suffer those horrors is very moving."

Mrs Thornton, 59, who has four children and four grandchildren, learned much of John's life from his baptism registration as a Christian in Marske on August 8, 1776.

He was described as a "negro servant" and was said to be about 17 or 18 years old.

It revealed he could say his catechism "in a tolerable way".

John's grandson George came to Bradford with his parents in 1835-36 during the time of the Chartist unrest and when there was an outbreak of cholera.

They lived in Furnace Street, Bolling Back Lane, which no longer exists. The two youngest members of the five siblings died in Bradford when only a few weeks old.