"I am a monk who has taken a vow of chastity, poverty and obedience," says Emmanuel Rousseau, one of 56 "professed knights" of the Order of Malta.
Founded during the Crusades as a military organisation that also ran hospitals, the world's oldest chivalric Order these days is engaged in providing humanitarian aid in crisis zones around the world.
On Saturday, one of Rousseau's colleagues in the top tier of membership will be chosen as the new leader of an Order whose last Grand Master, Britain's Matthew Festing, was ordered by Pope Francis to resign in January.
Rousseau, alias Fra' Emmanuel, has nothing in common with the traditional image of a monk dressed in sombre habit and cloistered away in a monastery.
He lives alone in a posh part of Paris, likes steak tartare and has a high-flying career at France's national archives.
The only clue as to his parallel life is the discreet, white Maltese cross he spots next to the button hole of his lapel.
His is an active life, just like colleagues who include a New York lawyer and an Italian doctor who studies the "miracles" associated with the French pilgrimage site of Lourdes.
But to honour his vows as a professed knight, Rousseau also devotes long hours to prayer, has already made over his residence to relatives, makes breakfast for the homeless and joins the sick and the afflicted on an annual pilgrimage to Lourdes.
- 'Modern and revolutionary' -
"It's about feeling a calling to live in the image of Jesus Christ," Rousseau says of his atypical vocation.
The tradition of the order, he explains, "is to seek an intense experience of the act of charity by putting yourself at the service of others, particularly the sick, and setting an example through the life you lead".
Rousseau's career as a knight has its roots in childhood, when his businessman father would take him to the Citeaux abbey in Burgundy. "I spent a week milking cows and listening to Gregorian chants," he recalls. Years as a boy scout also helped pave the way to his adult life.
With no inclination to become a priest delivering sermons to the faithful, he opted for the heritage business. After writing a thesis on Cistercian monks, he ended up supervising 380 kilometres of archives and some 200 staff.
Then, at 27, while helping the sick in Lourdes, something clicked. "I was paired with a member who had taken his vows and it was just as if we were joined as one." After years of charity work, Rousseau took his vows at the age of 41.
Until the end of the 18th Century, all the Knights of what is officially "The Sovereign Military Hospitaller Order of Saint John of Jerusalem of Rhodes and of Malta," took vows. At the time, to be a monk at the service of the sick was both modern and revolutionary, Rousseau says.
- Last of the Mohicans -
In 1798, when Napoleon took control of Malta -- the Knights' last bastion in the Mediterranean where they battled Muslim pirates to keep trade routes open -- there were still 2,500 religious knights in Europe.
Today, the 56 professed ones appear a little like the last of the Mohicans, lost amid an order of 13,500 members ranked by their noble titles and expected to lead an exemplary Christian life while participating in the charity activities of the Order.
Rousseau's family comes from humble farming roots but he has been given noble ranking to become one of the 11 members of the "Sovereign Council" that counsels and supports the Grand Master, who is still required to be born noble.
In the devout society of the 12th Century donations of land and farms to the Order were common and it remains one of the biggest landowners in Italy.
And the religious identity remains central today to donors who fund charity work in 120 countries, with one significant departure from its past.
The Order founded on what it saw as the need to defend Christendom from Islamic invaders and pirates is now involved in helping migrants around the world - including the many Muslims rescued in the Mediterranean.