ASK Francis Campbell whether he sees his appointment as Britain’s first Roman Catholic ambassador to the Vatican since the Reformation as controversial, and he laughs. “The Pope is a moral figurehead for the world, not just for Catholics,” he says. “The days when a Catholic could not represent the Queen to the Pope are long past.” But is he a devout Catholic? More laughter. “Well, I haven’t been to Santiago de Compostela on my knees.”

When Mr Campbell arrived in Rome last month, the airport reception committee did not at first recognise him, partly because he arrived on the low-cost airline Ryanair, but also because at 35 he simply looked too young for a job often given in the past to diplomats nearing the end of their careers.

But then Mr Campbell, with his Ulster brogue, sharp mind and an engaging manner, is breaking the mould in more ways than one. A farmer’s son from Newry, Co Down, he is the first Northern Irish Catholic to gain an ambassadorial post since Irish Home Rule.

When we met at the Villa Drusiana, the ambassador’s residence set near the Appian Way, he allayed fears that the British Embassy to the Holy See would be downgraded.

A year ago the Foreign Office announced that the new ambassador would be chosen by open competition, and would not necessarily be a career diplomat. The Embassy’s offices on Via Condotti — Rome’s Bond Street — have been closed, and the lease on the residence runs out this month.

Mr Campbell is no lightweight, however: recruited from Amnesty International, where he was senior policy director (a “career break” from the civil service), he previously served as First Secretary in the British Embassy to Italy. Before that he was an adviser on Europe in Downing Street, and had the sensitive job of organising Mr Blair’s visit to John Paul II in 2003, in the run-up to the invasion of Iraq.

Unmarried, he has a degree from Queen’s University Belfast in political science, an MA in European integration from the Catholic University of Leuven and another in international relations from the University of Pennsylvania. Hardly surprising, then, that the emphasis during his tenure will not be so much on garden parties as on “focused policy objectives”.

The move to premises within the compound of the Embassy to Italy has raised hackles in the Vatican, which insists that Britain’s Embassy to the Holy See and its Embassy to Italy must be kept separate. The Foreign Office justifies the move as a combination of financial prudence and “post 9/11 security concerns”. The Villa Drusiana is inconveniently far from the city centre, Mr Campbell says, and its domestic staff — now being laid off — cost money. “

Using restaurants is cheaper. Nineteenth century methods of diplomacy are no longer appropriate”.

A 1917 Foreign Office memo is said to have laid down that Britain’s representative to the Vatican (at ambassadorial level since 1982) should not be “in awe of the Pope”. All envoys until now have been non- Catholics. But British society has “changed dramatically in the last ten years”, he says. “The divide between Anglicans and Catholics held good for 400 years, but now there is a greater degree of pluralism in ethnic and faith communities. What we once thought were big differences turn out to be not so big after all.”

Yet surely some Britons will feel uncomfortable with a Catholic as “Our Man in Rome” — especially one who once considered entering the priesthood? “Well, some people will never be reassured. But we are taught to be detached. You might have a private view, but you have to look at things objectively.”

His faith, he insists, was not touched on at all in the application process, “apart from the fact that as ambassador you inevitably spend part of your time attending religious ceremonies. It would be pretty difficult to do the job if you had an aversion to religion”.

The three main issues he outlined to the Pope when presenting his credentials just before Christmas were dialogue between Christians, and between Christians and other faiths such as Islam; European enlargement; and development aid.

“There is lot of interest in London in knowing what the Vatican thinks. It has global reach. Look at the way the funeral of John Paul II became a magnet for world leaders.” Ten years ago, he says, Northern Ireland was the dominant issue, but after 9/11 the Christian-Muslim dialogue moved centre stage.

“For Britain, Islam is not an academic exercise; it’s about real communities it’s about what Britain is today. We, more than most, have something to bring to the table internationally.” I observe that in his address to the Pope he made no specific mention of Turkey’s EU aspirations, which — when Cardinal Ratzinger — the Pope tended to regard as a threat to Europe’s Christian identity.

“The British view is that we need Turkey in the EU both for Europe’s position in the world and for the sake of Turkish modernisation and democracy. Many Turks happen to be Muslims, but then every enlargement of the EU has been seen as some kind of dilution.”

The idea that Europe’s “Christian club” and Turkey’s Muslim population are incompatible is simplistic, he says. “Christianity in Britain is enhanced by contact with Islam. In many urban areas of Britain there is a melting pot of faiths. I do not see why that is not possible on a larger scale in Europe.”

The British response to John Paul II’s death, he says, “would not have happened 30 years ago. The old animosities have gone. The separation is increasingly not between subdivisions of faith but between faith and the lack of it.”

He believes that there is still a strong role for religion in British society. His “local parish church” in London is Westminster Cathedral. “When I look around at Mass there, I don’t see an ageing profile, I see a cross section,” he says.

Does he think Anglican-Catholic dialogue is stalled? “Well, there is no point in a bonhomie which doesn’t mean much. We have to find areas of understanding as well as division.” This year marks the 40th anniversary of Paul VI’s historic encounter in 1966 with the then Archbishop of Canterbury, Michael Ramsay. “I hope the coming celebrations will prove a milestone for further understanding.”

I put it to him that Catholicism under Benedict faces unresolved tensions on social, sexual and doctrinal issues, from women priests and celibacy to contraception and divorce. “Well, every international organisation runs the spectrum from progressives to conservatives. But beneath the tensions are common values.

“In any case I wonder if the gap is really so wide: I suspect it was wider in the Sixties and Seventies, in the aftermath of Vatican II. How to respond to rapid social change while staying faithful to tradition is a challenge for all faiths.”