Kennedy Ife had been having trouble sleeping. On the 13th of August, 2016, the 26-year-old and his family had been to a Chinese restaurant not too far from their home in Hadley Wood, an affluent north London suburb on the outer fringes of Enfield. In the days after, he started to complain of a sore throat, along with what was becoming persistent insomnia. He spoke about the need to "take a break" from their church – a worry to his deeply religious parents, who often attended Jesus Sanctuary Ministries, a charismatic Pentecostal church in south-east London.

Kennedy's behaviour grew increasingly disturbed over the course of the following days. On the 19th of August, a Friday, he threatened to cut off his penis, before shouting that he would rape a young girl. This provoked a fight with his father, which ended in Kennedy being forcibly restrained with cable ties. Later the same day, as tempers cooled, he was allowed out for a walk, accompanied by two of his brothers, Roy and Colin. But Kennedy quickly became agitated, taking his top off and throwing punches at Colin, before attempting to head-butt Roy. His brothers have said they were aghast; this was the first time they had ever seen behaviour like it from their sibling.

Returning home, Kennedy was quickly restrained. Lashed to a bed with cable ties, ropes and handcuffs, his brothers took turns to "guard" him as he railed against the serpent he believed to be inside of him (at one point, it's said that Kennedy shouted about the "mark of the Beast").

Two pastors from Jesus Sanctuary Ministries arrived to pray for Kennedy and attempt to exorcise the evil spirit they believed to be inside him. On Monday the 22nd of August, another of his brothers, Harry, phoned 999, saying that Kennedy was struggling to breath. By the time paramedics arrived, Kennedy was dead. The police officers who arrived shortly after found the Ifes attempting a resurrection. "Kennedy, I command you to rise in the name of Jesus," were the words they heard Colin Ife say as he stood by his brother's body.

Later, when on trial at the Old Bailey, Roy Ife told the jury that he didn't know that Kennedy was suffering from a "mental health episode". Under cross-examination, he said he believed his brother was suffering from a sore throat. But, as the disbelieving prosecutor pointed out, you wouldn't normally ask Jesus' help to clear up a scratchy oesophagus. The court heard that this was a case of exorcism gone wrong, and that visitors from the Ifes' church were actually there to try to expunge the evil spirit from Kennedy's body. On the 14th of March, 2019, seven members of the Ife family were found not guilty of manslaughter.

Photo: Adam Korzeniewski / Alamy Stock Photo

The belief that demons exist is as old as religion itself, but at the end of last year it was reported that exorcisms are back in a big way. In 2017, the Catholic rite of exorcism was translated into English for the first time since being standardised in the early 17th century, and in May of this year the Vatican held a dedicated "exorcist training convention" in Rome following a sharp rise in "reports of demonic possession around the world".

Looking into what's caused this current "spike" throws up complex answers. What's evident is that it isn't just a Catholic concern, as a 2017 report by faith-focused think-tank Theos made clear. The "Christianity and Mental Health" paper points to Pentecostalism – the Protestant renewal movement with an emphasis on direct personal connections to God – "[which is mainly] driven by immigrant communities and churches [which are] very open about their exorcism services".

The rise of Pentecostalism in the UK wasn't an overnight occurrence, though it grew mainly in the margins, in urban working class immigrant communities. In a 2006 report, Pentecostalism was listed as the fastest growing group of Christians in the country, with under 1 million adherents, though some believe that number to be much larger. In the USA, that figure stands at 20 million, with over 10 percent of all Christians worldwide thought to identify as Pentecostalist.

For millions of the devout – Pentecostalists, but also many others – evil is not a metaphor, but an active physical presence to be fought accordingly. As a recent piece in The Atlantic outlines, roughly half of Americans believe demonic possession is real, with over 70 percent believing in the devil. In the UK, the figures are much smaller, with even self-identifying Christians statistically more inclined to believe in aliens than Lucifer.

Dr Andrew Chesnut is Professor of Religious Studies at Virginia Commonwealth University and an expert on Catholic death culture and Latin American religion. He rejects my use of the word "spike" when describing the current rise in exorcisms, preferring instead to call it a "boom".

"[That's in both] Catholic and Pentecostal exorcisms, there's no doubt," he says when we speak over Skype. "This is due primarily to the latter influence, as by far the highest number of exorcisms [performed] on a daily basis across the globe are performed by pastors with no special training, unlike in the Catholic Church, where you need authorisation from your bishop. [This is the case] particularly in the global south, most importantly in Africa and Latin America."

What was formerly a practice confined mainly to the shadows became thrust into centre stage sometime in the 1970s, primarily due to the influence of the neo-Pentecostal movement, with its roots in Latin America. "[Exorcism] is still so popular in these churches, like The Universal Church of the Kingdom of God in Brazil, which reserves its Friday night services for exorcisms – though they don't call it that," says Dr Chesnut. "It's called 'liberation' or 'deliverance' instead."

He's clear that any discussion of exorcism needs to make an important set of distinctions. Catholic exorcisms are wrapped in centuries of tradition and accord to a rigid series of regulations. Though informal rituals do take place, they are rare and often undertaken behind closed doors. In theory, only an ordained priest or higher prelate can carry them out, and then only with express permission.

Differences aside, both Catholicism and Pentecostalism share exorcism as, if not a key tenet, then at least a significant one. There's the shared love of spectacle and ritual in both traditions, even if their substance differs wildly. That's one explanation for why the "boom" in exorcism remains broadly confined to the two strains of religion, though there have also been recent reports detailing an increase of Islamic exorcisms in the UK. The rise in Catholic exorcisms could perhaps even be thought of as a response to the threat of Pentecostalism to its "market share" in both the West and the "global south", where it has been in catastrophic decline since the 1970s.

Dr Kate Kingsbury is Dr Andrew Chesnut's research partner. Based at The University of Alberta, she is an expert on the global exorcism boom, and explains to me how Pentecostal traditions differ in approach to those performed by Catholic clergy.

"They are often extemporised and ad lib," she writes over email. "Any pastor can perform one, and even members of the laity may at times choose to undertake them. Due to the lack of a stringent, standard code, exorcisms may take on a plethora of forms and are usually far more dramatic than in the Catholic tradition, often taking on theatrical guises that draw in audiences from far and wide."

These are often spontaneous, public affairs with emotions running high – and have spawned several high profile controversies. Kate mentions the recent case of Pentecostal South African pastor Alph Lukau, who kissed a young girl during an exorcism: "Purportedly, it was in Jesus' name and to expunge a demon in her mouth. Such incidents may cause tension when Catholic clergy catch wind of them, as they may lambast such practices and their practitioners for improper procedural protocol."

The UK has witnessed several of its own scandals over the last 20 years. At the turn of the millennium, the murder of Victoria Adjo Climbié in London sparked national headlines and widespread revulsion. Her guardians believed – allegedly on the advice of their preacher at a branch of the Universal Church of the Kingdom of God – that the eight-year-old was possessed by satanic forces. The horrifying details are not important to relate, though the crime provoked radical changes to child protection laws in the UK.

In 2018, The Guardian ran an article detailing the anonymised recollections of three people who claimed they were the recipients of coerced exorcisms, somewhat baldly headlined "Like being raped". In the piece, 67-year-old "Sue" claims she underwent the ordeal at the hands of an agency doctor, at a London hospital. Another middle-aged man, "Chris", describes being physically restrained in his youth at a free church youth community group with Pentecostal links, and subjected to an exorcism ritual on account of his "demonic" homosexuality.

A Colombian boy screams of pain while supposedly being possessed by demons during an exorcism in Bogota. Photo: DPA Picture Alliance / Alamy Stock Photo

Exorcism is a difficult concept for the irreligious. For many, it's simply synonymous with cheap horror films or exploitation of the vulnerable. But it would be a lazy disservice to paint all of exorcism's uses with this same brush.

The American journalist Barbie Latza Nadeau has spent 20 years in Italy, covering everything from the Amanda Knox case to the refugee crisis and mafia activity in Naples, and attended the recent exorcism convention in Rome. Her 2018 book Roadmap To Hell is a work of dogged, sensitive reporting that tells the story of modern slavery and an underworld dominated by the Camorra and recently transplanted Nigerian drug gangs.

In the last decade, she writes, thousands of women have been trafficked directly into sexual slavery, predominantly from Nigeria, in the belief that they are travelling to Europe for jobs in hair salons or the hospitality industry. Once in Italy, it becomes apparent that the truth is much more sinister. Placed under the crushing bondages of an arbitrary debt for travel (often tens of thousands of Euros), they are sent out into the danger and unpredictability of the streets. Often, a black magic curse is placed upon the women in Nigeria before they embark for Europe. Belief in JuJu is widespread, and to fall foul of a curse could potentially mean harm befalling loved ones.

For those tasked with helping the women escape slavery, this presents a problem: a spiritual malady requires a spiritual solution, as some local members of the Catholic Church have discovered. In the face of an often indifferent state, which has left the women in a horrifying limbo, exorcism becomes one means of preparing the women to leave their bondage. It's less straightforward for the women who are not Christians, though Nadeau reports that Neapolitan exorcists try to follow JuJu rituals to the letter of their law, in order to fully convince their subjects that they are reversing the curse.

"If it works to free them, what's the problem?" poses one English Cardinal Nadeau speaks to after attending the exorcism of a deeply vulnerable young woman named "May".

The heat and drama of southern Italy feels a long way away on the overcast Sunday morning I shuffle down the backstreets of the Old Kent Road, in south-east London. About ten minutes walk from the din of the arterial thoroughfare, I arrive at Jesus Sanctuary Ministries, the same church attended by Kennedy Ife's family – a bland brick building lodged behind a cluster of industrial units.

I'd tried to arrange a talk with the church's head pastor, Pastor Uzor Ndekwu, but it proved difficult to pin him down. I understood his reticence to be questioned on the subject – one that could do little for his church other than bring bad publicity and unthinking suspicion.

Pastor Ndekwu is not the only person reluctant to speak on the topic. During my research, I find that people are often shy when it comes to talking about their personal involvement with the paranormal, particularly when it comes to exorcisms. It's an intimate, often frightening experience, and frequently a domain of the vulnerable – often people suffering from acute mental illness, or working through periods of deep and unresolved trauma.

This is a surprisingly under-explored topic in academia, though a 2012 study into the prevalence of "spirit possession" among former child soldiers in northern Uganda made the formal link between trauma and the dissociative symptoms often apparent with presumed demonic possession. It is, perhaps unsurprisingly, also not often a topic of public discussion for either Catholic or Pentecostal spokespeople.

Unable to interview any exorcists in person, I make Gert Brouwer's acquaintance through a Facebook group on paranormalism that describes itself as an "Association for Exorcism and Demonology". After weeks of messaging back and forth, he agrees to talk.

Gert was born and raised in Holland, and still lives in the small city of Breda, in the country's south, where he devotes his working life to the paranormal. His position is unusual, he tells me, as both a practitioner and recipient of exorcism. From childhood, there was always a sense of something beyond what his hands could grasp; something subtle and almost inexplicable. Then, at 21, he had his first "violent haunting", when he encountered a demon in his apartment. The experience left him shaken, but he also wanted to work out how to unravel it in a way that secular terminology couldn't manage. Years of study led Gert to the point that he feels confident in describing his ability to "communicate with the disembodied".

Gert is cautious about performing exorcisms, "as 99 percent of claims aren’t paranormal and only a tiny proportion of them are actual evil", and he considers aftercare as important as the ritual itself. He's spare with specifics and is keen to outline the need for experience and expertise in what – after all – is a profession of sorts, though he tells me he's entirely self-taught.

What his metrics are for determining "pure evil", or what exactly his aftercare consists of, are questions left unanswered, and it's impossible to not feel some vague unease – though it is difficult to doubt the sincerity of his convictions.

It's the middle of a dull, stolid Wednesday as I make my way to St Patrick's Church in Soho. The small cluster of congregants are spread thinly across the sprawling 19th century parish church; a mix of lunch hour drop-ins and kneeling tourists. It's difficult to make out the priest's words from the back of the hall, and I feel a semi-familiar embarrassment; what might be a hangover from robotic childhood observances, or just the act of intruding into other people's quiet.

It's hard to square the sleepiness on show with thoughts of demons and the living, stalking evil and possessed human beings. Turning to go, I light a couple of candles out of habit and make my way back out into the grey of the afternoon.