As the Vatican's chief exorcist, Father Gabriel Amorth was often asked to help people whose troubles turned out to be far more mundane than demonic possession.

However, he was convinced he faced evil incarnate one morning in 1997 when a young Italian man was brought to his small consulting room in Rome.

The peasant was accompanied by his priest and another man. The latter was a translator.

For while the afflicted man spoke only Italian, the evil spirit inside him spoke perfect English, he was told.

Father Gabriel Amorth (pictured), who was the Vatican's chief exorcist, was convinced he faced evil incarnate one morning in 1997 when a young Italian man was brought to his small consulting room in Rome

Fr Amorth started the exorcism in Latin and the moment he mentioned Jesus's name, the young man fixed his gaze on him and began to yell curses and threats in English, then spitting and making out as if about to attack him.

When the exorcist arrived at the prayer Praecipio tibi ('I command you'), the demon briefly went quiet.

'But then, screaming and howling, the demon burst forth and looked straight at him, drooling saliva from the young man's mouth,' writes Marcello ­Stanzione, a fellow Catholic priest who worked with Fr Amorth.

Fr Amorth continued the 'rite of liberation', demanding the demonic presence reveal its name. He was shocked when he was told it was Lucifer himself. Momentarily shaken to be confronting the Devil, he nevertheless ploughed on.

The possessed man resumed his shrieking, twisting his head back and rolling his eyes, his back arched for quarter of an hour. The room became extremely cold and ice crystals formed on the windows and walls.

Moments after the exorcist ordered Lucifer to abandon the peasant, the young man's body stiffened and began to levitate, hovering three feet in the air for several minutes before collapsing into a chair.

Finally, Satan admitted defeat, announcing the exact day and hour when he would leave the man's body. It sounds like the stuff of horror fiction.

For while the afflicted man spoke only Italian, the evil spirit inside him spoke perfect English, he was told. Pictured: A scene from The Exorcist

But Fr Stanzione insists it all happened. He has just written a book, The Devil Is Afraid Of Me, containing astonishing new details — including the horrific demonic encounter in 1997 — about the extraordinary life of Fr Amorth.

A man who was dubbed the Dean of Exorcists but who in the flesh looked more like a friendly tortoise than a grim vanquisher of evil, Fr Amorth said he conducted a staggering 60,000 exorcisms over a 30-year period.

The Pope's chief exorcist died aged 91 in 2016, prompting national mourning in Italy, where an estimated 500,000 people visit an exorcist each year.

Although as official exorcist for the diocese of Rome he was the Catholic Church's most famous and controversial exorcist, he was far from its only one.

There are at least 400 in the world. Even in the traditionally sceptical UK, the church says it is carrying out an increasing number of exorcisms.

Most of his colleagues prefer to practise their peculiar craft in the shadows — and the church, wary of ridicule, encourages that — but Fr Amorth was more than happy to discuss how he fought the powers of darkness.

The Bible records that Jesus himself drove out demons but provides few details, leaving ­Hollywood to fill in the blanks.

The terrifying 1973 film The ­Exorcist remains the go-to reference work, its story of a little girl transformed into a projectile-vomiting, blaspheming horror was loosely based on a reallife exorcism in the U.S. Fr Amorth said it was his favourite film, arguing that although the special effects were over-the-top, it was 'substantially' accurate and helped people understand his work.

The possessed 'isn't a bad person, only a suffering one,' he claimed.

The youngest of five sons of a lawyer in the town of Modena, Fr Amorth fought as a teenager in the Italian resistance in World War II (earning a bravery medal).

He later became a lawyer himself and briefly worked for the future Italian prime minister Giulio Andreotti before taking holy orders in 1951.

It was in 1986 that he became an apprentice exorcist and he went on to set up the International Association of Exorcists in 1990.

He initially conducted exorcisms in Rome's famous Church of the Holy Stairs until the shrieks drove away the faithful.

He then moved to the headquarters of his order, the Paulist Fathers, and converted a small, nine by 15ft room into his exorcism room — well away from the street so passers-by couldn't hear the screaming and call the police.

Half a dozen chairs lined the walls for his assistant exorcists and the afflicted's loved ones, and a worn-out brown velvet armchair for the patient.

Particularly troubled souls might have to be tied down with straps on a small bed.

The patient would always be violent so exorcists never practise alone.

The walls were decorated with eight crucifixes, pictures of Mary and one of the Archangel Michael, leader of God's army.

He would also have a photo of Pope John Paul II which apparently made devils 'particularly irritable'.

The priest kept the tools of his trade in an old briefcase: two wooden crucifixes, an aspergillum for sprinkling holy water and a vial of consecrated oil. He also used a purple priest's stole, wrapping it round the patient's neck, and a book of prayers containing the official exorcism formulae.

He was famous for his sense of humour — not the obvious prerequisite for an exorcist — and always started off each ritual by literally thumbing his nose at the Devil.

According to Marcello Stanzione, during an exorcism a demon accused him of being a glutton. 'Well, what's it to you?,' he shot back.

A favourite Amorth quip was to say: 'You know why the devil flees when he sees me? Because I'm uglier than he is.'

Although the Catholic Church officially recognises exorcism, its modernisers see it as a medieval hangover that plays on superstition to strengthen religious devotion.

Fr Amorth freely admitted many who came to him had mental problems best dealt with by a psychologist, and he estimated he only came across around 100 genuine cases of possession.

People came to Fr Amorth from as far away as the UK and Spain after having trouble finding exorcists closer to home. His exorcisms could involve a single straightforward prayer or take months and repeated ceremonies.

It could even take years. Early in his career, he helped an exorcist named Fr Negrini near Brescia, northern Italy, with a supposedly possessed 14-year-old girl.

When Fr Amorth joined Negrini in a session with the girl, the latter asked the demon: 'Why have you taken this girl.'

It replied: 'Because she is the best of the parish.' It took Negrini another 12 years to free the girl, says Stanzione. Fr Amorth would carry out some exorcisms on the telephone and even on Skype.

Appointments lasted on average 30 minutes and Fr Amorth could conduct five every morning, doing paperwork in between.

Typical symptoms of demonic procession could be mundane, such as violent headaches and stomach cramps, he said, so it was easy to confuse it with an ordinary illness.

He often wouldn't know for sure until he had conducted the rituals and observed the reaction. He said the Devil particularly hated hearing Latin and often preferred to speak in English, even when the possessed person couldn't usually speak a word of it.

They also liked to spit — experienced exorcists hold a cloth near their face in readiness — and, rather more alarmingly, vomit shards of glass or pieces of iron, and even rose petals.

Fr Amorth kept a collection of regurgitated nails, keys and plastic figurines to prove it.

On one occasion, he claimed a devil said a possessed woman would bring up a transistor radio and, sure enough, she began spitting out pieces of it. Almost supernatural strength was not infrequent.

Fr Amorth said he once saw a possessed boy of 11 hurling off three big policemen as they tried to hold him down and a ten-year-old pick up a huge table.

How did all these unfortunates come to be possessed?

In 90 per cent of cases, Fr Amorth blamed Satanists or 'someone who has acted with Satanic perfidy'.

The remaining cases he blamed on people participating in practices such as seances.

Most of those he saw were middle-aged women, a fact he blamed on their weakness for seeing fortune tellers, who remain very popular in Italy.

Just months before the priest's death in 2016, William Friedkin — the Oscar-winning director of The Exorcist — became the first person to be allowed to film him perform an actual exorcism.

The resulting documentary makes for unsettling viewing as the patient, an Italian woman in her late 30s, thrashes violently, shouting defiance in a guttural voice that — for whatever reason — simply doesn't sound human.

Fr Amorth believed the woman was genuinely possessed, after being cursed by her brother and his girlfriend, who were satanists. Friedkin, an agnostic who hadn't expected to see anything authentic, said the experience was 'terrifying'.

Top neurosurgeons and psychiatrists he showed his film to were genuinely flummoxed. Cynics might wonder why only those who genuinely believe in the Devil seem to be possessed by him.

For Fr Amorth, who railed against the scepticism of the modern age, such cynicism suits Lucifer just fine.

'The Devil is always hiding,' he warned, 'and the thing he wants above all is that we don't believe he exists'.