"I was quite chuffed. I felt like royalty myself. I've never spoken to anyone in New Zealand who's said they've got a relative buried in Westminster Abbey," said Williams.
Williams' great-grandfather Thomas Prior immigrated to New Zealand in 1851.
Many members of Williams' family say Thomas Prior was a descendant of the brother of Matthew Prior, who is thought to have never married nor had children.
Some of the family have travelled to England to meet other members of their family tree and the link has been confirmed by them too.
According to the papers and biographies online, Matthew Prior was taken as an orphan into the care of his uncle who was a fashionable wine merchant.
There he was found by the Earl of Dorset reading Horace.
The Earl was impressed and made a contribution to Prior's studies at Westminster and the "shop boy" later earned a scholarship to Cambridge.
From there Prior held various diplomatic roles in the Netherlands and France.
Working as an embassy secretary in Paris, Prior found favour with both Queen Anne and Louis XIV.
He was later arrested due to his links to the Tories when the Queen died and the Whigs regained power.
Williams said he'd come close to getting his links to Matthew Prior royally checked out in 2015, when Prince Harry was in Whanganui.
"He was meeting the returned servicemen at the memorial hall. I was hoping to talk to him about it and if he could get someone to check it out," he said.
"They put me on the first table when he jumped down ... but he stepped down and made up his mind to go around the other way ... I would have been the last person he saw.
"Then the call came over to say the visit had been cancelled early ... the weather had packed in in Auckland and the prince is flying there ... so that was the end of that.
"It was a terrific opportunity to find out something."