King Charles and Queen Camilla paid a surprise private visit to a convalescing Pope Francis on Wednesday afternoon during their four-day state visit to Italy.

The royal couple visited Francis, 88, at his home in Casa Santa Marta in Vatican City, where he is recovering from a serious bout of pneumonia in both lungs. An official audience had previously been removed from the royals’ schedule due to the pontiff’s ill health.

The Vatican said in a statement that during the meeting the pope expressed his best wishes to Charles and Camilla on their 20th wedding anniversary, which they celebrated on Wednesday, while they wished for his “speedy recovery”.

Buckingham Palace said Charles and Camilla “were delighted the pope was well enough to host them – and to have had the opportunity to share their best wishes in person.”

Francis was discharged from Rome’s Gemelli hospital, where he spent five weeks being treated for the life-threatening pneumonia, on 23 March. His medics said he would need to convalesce at home for at least two months.

The meeting on Wednesday came after Charles became the first British monarch to address a joint session of the Italian parliament, surprising many politicians with his Italian language skills.

The king joked that he hoped he wasn’t “ruining” the language of Dante to the point that “he would not be invited to Italy again”.

“Italy is a country very dear to my heart and to that of the queen, as it is to many British people,” he said.

The couple met the Italian prime minister, Giorgia Meloni, earlier on Wednesday and are being hosted by President Sergio Mattarella for a state banquet at the Quirinal Palace on Wednesday night. They will travel to Ravenna, in Emilia-Romagna, on Thursday before returning home.