Camilla, Duchess of Cornwall, poses for photographers before attending a banquet at Buckingham's Palace in London, in honour of Norway's Crown Prince Haakon and Crown Princess Mette-Marit who are on a three-day official visit to mark their Nordic nation's 100 years of independence. (AFP)

Camilla, the new wife of Britain's Prince Charles, wore a royal tiara for the first time at a banquet honoring the visit of Norway's King Harald V.

It is the first time that Camilla has attended a royal banquet, having married Charles, the heir to the British throne, in April.

Harald and his wife Queen Sonja are in London for a three-day visit to mark the centenary of Norway's independence from Sweden.

The glittering tiara was loaned to Camilla by Queen Elizabeth II, who is thought never to have worn the priceless piece.

The ring of brilliant-cut diamonds mounted in gold and set in platinum was created in 1911, and previously worn by Queen Mary -- the present queen's grandmother. She wore it in Delhi, India in 1911 to mark the start of her husband King George V's reign as king of England and emperor of India.

Camilla was dining with the queen, the Duke of Edinburgh and the Prince of Wales in the Ball Room of Buckingham Palace.

Her seat was in a prime position next to the King Harald at the middle of the top of the lengthy horseshoe shaped banquet table. Harald was also placed next to the queen.

Accompanying the king and queen of Norway was Crown Prince Haakon and his wife Crown Princess Mette-Marit, who is eight months pregnant.

Prime Minister Tony Blair was among the 160 guests along with his wife Cherie, Foreign Secretary Jack Straw and the Archbishop of Canterbury, Rowan Williams.

Guests were required to wear evening dress, full ceremonial dress or national dress for the occasion, with royal ladies required to wear tiaras.

(Agencies)