Genealogists have discovered a distant "rags to riches" Irish cousin of Prince William on a unique 19th century document dedicated to an English lord.
The artefact - known as the Morpeth Roll - contains the signatures of more than 160,000 Irish people paying tribute to George Howard, or Lord Viscount Morpeth, when he left his post as chief secretary of Ireland in 1841.
It measures 420 metres (1,378 feet) - three times the length of Dublin's Croke Park stadium - and is being published online after a four-year project to digitise the testimonial.
Researchers trying to uncover the stories behind the signatories, including aristocrats, merchants, politicians and clergy, discovered the connection between Britain's royal family and a man on the roll called Henry White, from Booterstown, south Dublin.
One of three brothers, Mr White's great-grandson Luke Henry White married Lavinia Spencer, sister to Princess Diana's grandfather Albert Spencer, in 1919.
Deirdre Watters, of National University of Ireland Maynooth, which worked on the project, said the link was only discovered in recent days and research was ongoing.
"Henry's father Luke White appears to have made his money in publishing companies," she said.
"We think his is a bit of a rags to riches story. They would have been nouveau riche at the time."
As they rose to prominence the Whites bought Luttrellstown Castle, on the edge of Dublin's Phoenix Park, where David and Victoria Beckham got married.
The Morpeth Roll was a rare tribute to an English administrator in Ireland.