When Arnold Awoonor-Gordon moved into his terraced house in Chatham 25 years ago, he could never have known how close he was to finding the missing link between a family legend and one of the most extraordinary stories of Victorian England.

Arnold, 83, had learnt stories from his great-grandmother Emily of how his great-great-grandmother had been saved from the slave trade in Africa – and became the adopted daughter of Queen Victoria.

The retired radio broadcaster had assumed they were the ramblings of an old lady, but curiosity got the better of him when he arrived in this country from Sierra Leone.

A phone call to Windsor Castle confirmed it was true and, fired with enthusiasm, he delved deeper to discover, by an incredible coincidence, that Sarah Forbes Bonetta had at some point lodged in Gillingham with the monarch’s approval.

For years Arnold had scoured history books and old royal records and made countless trips to the library – but to no avail.

Then, a few weeks ago, TV researchers making a documentary of the woman now known a The African Princess, informed him that they had tracked down where she had lived.

To his amazement, it was in Canterbury Street – about a mile away from his home in Luton and in a road he has walked along on numerous occasions.

Arnold, of Cobden Road, said: “I am in my 80s now and I had given up finding the house. I knew the name Palm Cottage and there was a social club of that name.

“But I had no idea there was a cottage tucked behind. I thought, being well over a hundred years ago, it would have changed name or have been knocked down.”

Arnold has returned to the cottage with the BBC television crew, where he unveiled a memorial plaque.

Bonetta was put in the care of the Rev Frederick Scheon and his wife, who were both church missionaries and had a daughter the same age, in her late teens.

She lived there between 1855 and 1861, then married a wealthy African businessman at a grand ceremony in Brighton.

For Arnold, finding Palm Cottage was the final piece of the jigsaw in the life of his illustrious great-great-grandmother.