The King and Queen have released three official photographs to mark their 20th wedding anniversary.

The royals were pictured smiling, soon after arriving in Rome for the start of a four-day state visit to celebrate ties between Britain and Italy.

The couple were photographed at the Villa Wolkonsky, the official Rome residence of Edward Llewellyn, the UK’s ambassador to Italy and San Marino, after their government jet landed at Ciampino Airport with an F-35 fighter jet escort.

In one image the King and Queen, who is wearing an Anna Valentine white and beige coat, are in the grounds of the home. In the other photographs, they are pictured near the Neronian arches, a branch of the Aqua Claudia, a Roman aqueduct supplying Rome.

The Queen also wore a Faberge lily-of-the-valley brooch reportedly given to the the late Queen Mother by Soviet leader Nikita Khrushchev during his official visit to Britain in 1956.

The King and Queen pose for a portrait at Villa Wolkonsky, in Rome. Photo: Buckingham Palace

The King and Queen will spend their 20th-wedding anniversary night as guests of honour at a state banquet held in Rome.

They are expected to be joined by leading figures from Italian life at the black-tie dinner, held as part of the royal couple’s state visit.

The head of state and his consort wed in a civil ceremony at Windsor Guildhall on April 9, 2005, following a romance that began when they were in their early 20s.

The King first met fun, confident Camilla Shand on the Windsor Great Park polo field in 1970, when he had just left the University of Cambridge, a year before he joined the Royal Navy.

Despite the pair’s closeness, there was no marriage proposal. When their relationship cooled after the then Prince Charles pursued his Navy career, Camilla wed cavalry officer Andrew Parker Bowles in 1973.

In 1981, the prince married Lady Diana Spencer, later Diana, Princess of Wales.

The then Prince Charles and Camilla on their wedding day in 2005. Photo: AAP

After the breakdown of both marriages — and Diana’s death in 1997 — Camilla’s eventual emergence as the then Prince of Wales’ long-term partner was part of a carefully planned PR campaign masterminded by the heir to the throne’s spin doctor Mark Bolland.

Their first public appearance together came outside the Ritz hotel in London in 1999 and was dubbed Operation Ritz. They faced a mass of waiting photographers, who had been tipped off.

At their wedding reception, held the same day as the Grand National, the King’s mother, the late Queen Elizabeth II, said about their romance: “They have overcome Becher’s Brook and The Chair (two fences in the famous steeplechase race) and all kinds of other terrible obstacles. They have come through and I’m very proud and wish them well.

“My son is home and dry with the woman he loves.”

-with AAP