Born in Maidenhead in 1923, brought up in Mexico where his father worked for Shell and educated at Hurstpierpoint College in Sussex, Pogson had volunteered for the Navy at the start of the Second World War. He sailed with North Atlantic convoys before being promoted to the rank of lieutenant- commander and being given the command, at the age of just 22, of a minesweeper in the Adriatic.
"Knowing my mother," says Jonathan Doria Pamphilj of their meeting, "I expect she gave him no indication at all of her family background. In fact, he may not have realised exactly who she was until years later, when he came to visit her in Rome."
Drawn together by a shared interest in Catholicism - Pogson had converted at the age of 18 - the two cemented their friendship in a 14-year correspondence. Then in 1958 Pogson - a Shell employee at the time - changed his name by deed poll to Doria Pamphilj before marrying his long-time flame in the Brompton Oratory.
The union received the blessing of Orietta's father, who himself had married an Englishwoman in a family tradition which dates back to 1830. Prince Filippo insisted only that Pogson take the family name before marrying the last of the line. The prince died before the wedding took place, leaving the newly weds to face crippling death duties and to cope with a huge estate badly in need of refurbishment.
Pogson Doria Pamphilj rose to the challenge, throwing himself into the administration of the properties, and having the family's gallery in the Palazzo Doria Pamphilj in central Rome rewired and refloored to provide a suitable home for the priceless collection of Titians, Caravaggios and the stunning Pope Innocent X by Velzquez. Moreover, he broke with tradition and had the dust sheets taken off the palace's private apartments, opening them up to the public for the first time.
In the small, provincial, conservative Rome of the 1950s, the task facing the English interloper was not an easy one. "He had to learn the language, and, more importantly, he had to learn how things were done here. It can't have been easy for him," says Jonathan.
Though he threw himself into his new Roman life with a vengeance, Pogson Doria Pamphilj also held on firmly to his British roots, setting up the cricket club which met each Sunday at the Villa Doria Pamphilj in the north of Rome ("though my father hated cricket," recalls Jonathan) and working hard to encourage good relations between the Catholic Church and the Anglican Church which he had left so many years earlier. Rome's Anglican Centre is based in the family's Rome palace.
His new life style gave Pogson Doria Pamphilj an opportunity to indulge his great passions, for music, sailing, and history which he had longed to study at university, a desire stymied by his father who insisted he left education and earned a living.
"He would have historians around here and they'd sit and talk for hours," Jonathan says. "Then there was music: he loved music, and any musicians passing through Rome would be invited home too."
One long-time resident in the huge complex of apartments inside the Palazzo Doria Pamphilj recalled Frank Pogson as "one of the kindest men I ever met. He was warm and witty and had a knack of understanding people's needs."
Frank Pogson Doria Pamphilj died after a long illness. He was at the lunch table at the time, laughing at a joke with an old friend.
Frank Pogson: born Maidenhead, Berkshire 6 September 1923; changed surname by deed poll 1958 to Doria Pamphilj; married 1958 Princess Orietta Doria Pamphilj (one adopted son, one adopted daughter); died Rome 2 October 1998.