The three-sided screen will shield Charles when he is anointed with holy oil, consecrated in Jerusalem, on his hands, breast and head, shortly before he is crowned at London's Westminster Abbey on May 6.

Buckingham Palace said it was historically regarded "as a moment between the sovereign and God" with the screen there to protect its sanctity.

"Previously, it was a canopy over the top, which actually didn't provide real privacy, it was more figurative," said Nick Gutfreund, who designed and created the frame. "Now this three-sided screen provides absolute privacy."

There had been speculation Charles might allow people to see the anointing, but royal historian Professor Kate Willliams said that would have been a surprise.

"It is such a private, sacred moment," she told Reuters "It's a mystic moment."

The Palace said the screen was made using a combination of traditional craft skills and modern methods, and measured 2.6 m (8.5ft) high and 2.2 m (7.2ft) wide, featuring wooden poles topped by bronze eagles gilded in gold leaf.

Its central design, selected by Charles, is a tree with the names of all 56 countries of the Commonwealth, the international organisation which he also heads.

It was inspired by a stained glass window at the Chapel Royal of St James's Palace which was gifted to the late Queen Elizabeth to mark her Golden Jubilee in 2002, and it uses sustainable materials for the embroidery in keeping with the king's long-standing environmental campaigning.

Meanwhile, the poles were made from a windblown tree, which had originally been planted by the Duke of Northumberland in 1765 on the king's Windsor estate, west of London.

"It's utilising stuff that might have been used as firewood but actually we're using it for something very special," Gutfreund said. "We didn't want to spend money on things that aren't actually going to be reusable."