In line with Royal tradition, Welsh gold is being used for the rings, which will be plain in design.

The gold comes from the appropriately named mine in Trawsfynydd, north Wales.

The rings, made to a design chosen by the couple, have been crafted by The Crown Jeweller, David Thomas, of royal jewellers Asprey & Garrard.

Mr Thomas said it was a "great honour and privilege" to make the rings.

He said: "The rings took two or three days to make, which is a normal length of time for wedding rings."

Royal nugget

Mr Thomas, 56, said he would watch out for them when he followed the wedding on television.

But he would not reveal whether they had been engraved with any message.

"That has to remain personal," he said.

He said the wedding bands were now safely under lock and key in a secret location.

The rings worn by the Queen Mother, the Queen, Princess Margaret, Princess Anne and the late Princess of Wales were all made from the same nugget of gold, unearthed at Clogau St David's mine, in Wales.

Recent discovery

Gold from the Prince Edward mine has already found its way into the Royal treasury, when regalia for the investiture of the then Prince of Wales Edward was created from it in the 1920s.

The mine was named Prince Edward after the man who was later to become King Edward VIII.

The gold to be used for Saturday's wedding was discovered during recent exploration by Cambrian Goldfields Ltd and refined by Marple Laboratories, in Birmingham.

John Mason, a geologist with Cambrian Goldfields Ltd, said: "We offered the gold to the Royal Family after the announcement of the engagement and they graciously accepted."