The King and Queen will begin a four-day state visit to Italy on Monday, following his unexpected hospital stay last week.

The royals will visit Rome and the city of Ravenna, as they use the “soft power” diplomacy of the monarchy to strengthen Britain’s relationship with its ally.

A separate state visit to the Holy See in the Vatican has been cancelled as Pope Francis continues to recuperate after leaving hospital following treatment for double pneumonia.

With several Vatican events removed from the royals’ itinerary in Rome, the remaining engagements in the Italian capital have been spread over two days, and extra elements added to some engagements.

At the weekend the Pope made a surprise appearance in St Peter’s Square, in the Vatican. He appeared with an oxygen tube under his nose and was using a wheelchair.

The visit also follows the King’s brief hospitalisation in London last week due to side effects from his cancer treatment.

The 76-year-old monarch has been undergoing treatment since he was diagnosed with an unspecified form of cancer in February last year, following tests after a corrective procedure for an enlarged prostate.

Last week’s hospital stay, which led to the cancellation of engagements last Friday, was described royal sources as a “minor bump in the road”.

In Italy, the King will become the first British monarch to address both houses of parliament – the chamber of deputies and the senate of the republic.

He will also hold audiences with President Sergio Mattarella and Prime Minister Giorgia Meloni, and he and the Queen will attend a black-tie state banquet at the Palazzo Quirinale, hosted by the president on the evening of their 20th wedding anniversary.

Britain and Italy’s defence co-operation will be marked by a joint flypast over Rome by the Italian air force’s aerobatic team, Frecce Tricolori, and the RAF’s Red Arrows.

In Ravenna, the King and Queen will attend a town hall reception to mark the 80th anniversary of the province’s liberation from Nazi occupation by allied forces, on April 10, 1945.

They will celebrate literary culture by visiting Dante’s tomb and the Queen will make a solo trip to the Byron museum.

-AAP