A solemn Mass has been held to remember the grand master of the order of the Knights of Malta, a Catholic order that traces its origins to the Crusades.
Fra' Bertie extended the order's humanitarian work
His Most Eminent Highness Fra' Andrew Bertie was the first Englishman to lead the order since the 13th Century and was grand master for almost 20 years.
Italy's President Georgio Napolitano was among numerous guests present at the commemorative service in Rome.
The non-political order runs relief operations in 120 countries.
It is supported by 80,000 volunteers and is well known for the work it does in many Muslim countries.
Fra' Bertie, the late prince and grand master of the order of the Knights of Malta, was remembered as a man of enormous charm and dignity.
He was on the one hand very British but on the other hand, he spoke six languages and [he was] a very international man
In 20 years as the grand master, the former school teacher had transformed the order, bringing a fresh approach to the humanitarian work, and extending it to some of the world's most inaccessible regions, says the BBC's Christian Fraser in Rome.
Under his leadership, the order extended its bilateral relations from 49 to 100 countries, and on Friday many sent their representatives to Rome to pay Fra' Bertie their respects.
The Basilica dei Santi Bonifacio e Alessio, on Rome's ancient Aventine Hill, was filled with 650 guests, diplomats, heads of state, 12 cardinals and a member of the British royal family, Princess Michael of Kent.
Also present were the senior members of the order, dressed in their fine black robes embroidered with a white eight-pointed cross.
One mourner said: "He was an extraordinary man in the sense that he was on the one hand very British but on the other hand, he spoke six languages and [he was] a very international man."
The order will meet next Tuesday to select Fra' Bertie's successor. Grand masters, like popes, are elected for life.
Fifty people will vote in the secret ballot and all the votes cast will be destroyed.
The voting continues until one candidate has a simple majority plus one.
The result will stay secret until the new grand master has revealed his identity to the Pope.