During a visit to William Cowley Parchment Makers, the company’s general manager told the Duke: “If Prince Harry marries Meghan then his certificate will be in our vellum.”
Prince William avoided commenting but opted for an awkward laugh before moving the conversation along.
Speaking afterwards, Paul Wright who spoke to the Duke said the Prince laughed, but it was a “nice laugh.”
The Queen must give formal consent for a royal marriage, and this consent is made in a calf-skin document called the “instrument of consent”.
The document is made in Milton Keynes by William Cowley Parchment Makers.
Paul Wright said: “Any member of the royal family needs the permission of the Queen. It’s called the instrument of consent.
“There were instances where members of the royal family were marrying prostitutes – you can’t have that.
“We’re very lucky because we’re the only ones in the world so it could never be anyone else.
“It’s also certain acts of Parliament but not all acts of Parliament.
“If you do it on paper if you’re really, really lucky you get about 350 years – with this we’re talking 5,000 years plus.”
Prince Harry and Meghan Markle made their first official appearance together in public at the Invictus Games on Monday.
Attending a wheelchair tennis match, Harry and Meghan arrived hand-in-hand at the venue and watched the sporting action from the stands.
The fifth-in-line to the throne and his actress girlfriend spoke to some of the athletes and those who were also spectating the tennis.
After the event came to an end, Meghan shook the hands of children who were spectating in nearby seats.
This appearance is significant as it marks the first time Prince Harry has taken his girlfriend of 18 months to an official event.
It will further spur rumours that the pair will soon become engaged.
