In an unprecedented move an Englishman has been elected for the second time running as Grand Master of the Knights of Malta, the Roman Catholic order which traces its origins to the Crusades nearly a thousand years ago.

Fra Matthew Festing OBE, 58, an art expert and former army officer who leads the order in Britain as Grand Prior and is regarded as a forward looking reformer, was chosen today. The secret ballot took place today at a papal-style conclave in the Knights' secluded headquarters on the Aventine Hill in Rome.

The Knight's inner council, dressed in black robes embroidered with a white eight-pointed cross elected the new leader of the order of the Sovereign Military Hospitaller Order of St John of Jerusalem of Rhodes and of Malta, as the Knights are also known. The 79th Grand Master, with the title "His Most Eminent Highness", takes over an organisation which is noted for its humanitarian work in conflict zones.

The order is also fighting a campaign to dispel the "myth" that it is rich, powerful and secretive. The election took only a few hours, seen as a sign of unanimity over reported plans to make the order more "open and transparent" and better known globally for its charitable and medical relief operations in 120 countries.

Grand Masters, like Popes, are elected for life. The move was announced after it had been approved by Pope Benedict XVI. It comes a month after the death of Fra' Andrew Bertie, a former schoolmaster and descendant of the Stuart dynasty who was the first Englishman to lead the order and served as its Grand Master for nearly 20 years.

Under his leadership the order - which has the status of sovereign state, with its own passports and stamps - expanded its diplomatic relations from 49 to 100 countries. The order has 12,500 full members, of whom only 50 are "professed knights" who take monk-like vows of poverty, obedience and chastity.

The order said that the new Grand Master "affirms his resolve to continue the great work carried out by his predecessor". It added: "Fra' Matthew comes with a wide range of experience in Order affairs. He has been the Grand Prior of England since the Priory's re-establishment in 1993, restored after an abeyance of 450 years. In this capacity, he has led missions of humanitarian aid to Kosovo, Serbia and Croatia after the recent disturbances in those countries, and with a large delegation from Britain he attends the Order's annual pilgrimage to Lourdes with handicapped pilgrims."

He was educated at Ampleforth and St John's College Cambridge, where he read history. As a child he lived in Egypt and Singapore, where his father, Field Marshal Sir Francis Festing, Chief of the Imperial General Staff, was posted. He is also descended from Sir Adrian Fortescue, a Knight of Malta martyred in 1539.

Frà Matthew served in the Grenadier Guards and holds the rank of colonel in the Territorial Army. He was appointed OBE by the Queen and served as Deputy Lieutenant in Northumberland. He joined the order in 1977, taking solemn religious vows in 1991.

A spokeswoman for the order said he was noted for his "very British sense of humour" as well as his passion for the decorative arts and encyclopaedic knowledge of the history of the Order.

Fra Matthew has promoted the teaching of Christianity in schools, observing that "We live during a strange period in history when children are taught "Comparative Religion" and leave school believing it does not matter what religion you profess .....No wonder many young people are astonished that anyone could possibly have been prepared to suffer and die for the faith".

At one time the order, which is predominantly male, was drawn from European aristocratic families. This has led conspiracy theorists to paint it as a rich and powerful cabal given to arcane rituals.

However Albrecht von Boeselager, the Grand Hospitaller in charge of the order's humanitarian arm, said this was "completely untrue". Charges that the order was conducting a secret "New Crusade" in Muslim countries and had sent mercenaries to fight in Iraq or Afghanistan were also "absolutely without foundation".

He added: "This kind of talk endangers our volunteers in the Muslim world. In Bethlehem we have a maternity hospital which delivers 3000 babies year, 80% of them Musulim. We are Catholic but neutral".

Winfried Henckel von Donnersmarck, a member of the order's Sovereign Council, said the order had 80,000 volunteers and spent £500 million a year helping the world's poor. "The only mystery is one of history. Any organisation is going to have mysteries if it has a thousand years of history behind it " he said.

He said women played a growing role, with Noreen Falcone recently becoming the first woman head of the order's national association in the US.

On its website the order's British chapter notes that there were English knights from the time of the First Crusade, with two priories established in the twelfth century , one for England, Wales and Scotland, and another for Ireland. The Grand Priory of England "received a great accession of wealth and property when the Templars were suppressed in 1312."

The order was disolved by Henry VIII in 1540, when several prominent Knights of Malta were executed. The Grand Priory's ecclesiastical seat is the Church of St. John of Jerusalem in St. John's Wood in London. It is separate from the Most Venerable Order of St. John of Jerusalem in the British Realm, founded in 1888, but the two bodies signed a co-operation agreement in 1963.