I was alerted to the Love School Event by huge adverts plastered on the side of buses and on the Rainbow Theatre, near my home in Finsbury Park, London. You might have seen them. They showed a square-jawed man with a glossy blonde woman. They looked a bit like a politician on the make and his loyal society wife. It wasn’t clear whether they were connected with the event they were publicising at Wembley Arena, or simply stock photos of the kind of romantically fulfilled people you could become if you attended. A bit of both, as it turned out.

The posters revealed little information about what the Love School Event, scheduled for a Sunday afternoon in late September, actually was – except that it was “not a religious event”. Intrigued, I headed to Wembley hoping to be told how to be a less disappointing boyfriend – bringing it in line with many other Sunday afternoons. As a cheap hack I went on a free press ticket, so there was a press conference beforehand.

If you were looking for reassurances that the organisation was transparent and laid-back you would not have found them here. Our questions had been sought and screened in advance, so that when we arrived we were presented with a piece of cardboard printed with what we were allowed to ask and in which order we were to ask it.

That loving feeling: more than 11,000 packed into Wembley Arena for the event. Photograph: Dave Bird

The hosts of the Love School Event were Renato and Cristiane Cardoso: the couple from the posters and paragons of their own advice. Renato – a charismatic speaker with a neatly trimmed beard – is a bishop in the Universal Church of the Kingdom of God (UCKG), a “neo-Pentecostal” group from Brazil. Cristiane is his wife of 23 years, co-author of the bestselling book Bulletproof Marriage and the daughter of the UCKG’s founder, self-styled Bishop Edir Macedo. Since it was founded in 1977, the church has gained more than 12 million members in 200 countries and, according to Forbes magazine, made Macedo a billionaire. The recent Brazilian presidential elections proved that it was a political force – in the run-up to polling day, President Dilma Rousseff appeared alongside Macedo at the church’s new £130m, 10,000-capacity replica of the Temple of Solomon in São Paolo. Along the path to the political mainstream the UCKG has been subject to persistent accusations of impropriety, almost invariably unproved.

I didn’t know any of this when I sat down at Wembley to ask Renato why the Love School Event was needed in Britain. “From 2016, most babies in the UK will be born out of wedlock,” he explained. “Marriage is going down and divorce is going up. I fear what will happen in 10 to 15 years. We don’t talk about our marriage problems – we are so quick to judge other people’s issues, and then for ourselves we make excuses. Porn is another threat, and so is Hollywood. Hollywood has disgraced families, and people are hooked on what Hollywood teaches.”

When Renato and Cris went backstage to prepare, we were introduced to some “real people” who had benefitted from the Love School and from the UCKG’s teachings more generally. I spoke to Talshan Thompson, 25, now working as a manager at Tesco and sporting a natty Malcolm X-style bow-tie and suit combo. “I was born in Jamaica, but moved here when I was 12,” he explained. “I didn’t really have a home growing up, and I ended up raising myself: washing my own clothes, cooking, taking myself to school. I didn’t really know what it meant to be a man. I was drawn into a gang. I didn’t believe in God.

“Before I came to the HelpCentre people were telling me that it was a cult, but I didn’t have any money. I didn’t really have a home. I didn’t have anything to lose. I wanted to see what was going on. My belief came gradually. I used to go out raving and get drunk, now I’ll have a drink at dinner, but I won’t test my limits. I want to come home with my wife.” It was hard not to be impressed by Talshan’s story, even if he was chosen to impress us.

Stage presence: the event lasted for three hours. Photograph: Tracy Howl

We filed in for the main event. Renato and Cris walked onstage under a shower of fireworks and embarked on a three-hour lecture structured around seven common relationship sins. The main lessons for men were: stick to your wife, don’t watch porn, generally don’t be a douchebag. For women: don’t put out too easily, don’t settle for lower standards of behaviour. Renato did about 90 per cent of the talking, now and then turning to his wife to offer her the chance to reiterate what he had just said.

Evidence for their points was a mixture of non-science and aphoristic philosophy. “I’m not criticising the women’s revolution, but…” Renato said at one point, before doing an impression of a woman getting hysterical about not cooking and wanting to be taken to a restaurant. Later he compared money directly to matrimony. “I’ve never seen a poor person who hates money,” he said, tearing up a fake £50 note to gasps from the audience. “But when marriages fail, couples blame marriage.”

The Love School wasn’t as interactive as I’d hoped, but there was some on-point prop work. Renato compared sex with milk, illustrating his point with a life-size model cow. “Before, if men wanted sex, they had to work for it. But now women see sex as a way of getting a man to like them. It’s like with milk. Before, if you wanted milk, you had to keep the cow, house the cow, feed the cow. Now you can just buy it from a shop. Why would a man go to all of this expense to get a woman if he can get all the milk for free?” In the context I am sorry to report that the audience lapped it up.

Shortly afterwards, Renato asked us all to dip into our pockets for the UCKG. He and Cris weren’t being paid for this show, he explained, surprisingly given who his father-in-law is. Tickets for the event had also cost up to £46.50. Almost all religious groups find ways of raising money from their congregations, of course, but there was something odd about the prominence of money in the lecture.

Heaven’s above: UCKG’s new church in São Paolo – a £130m, replica of the Temple of Solomon. Photograph: Getty Images

I left mulling over what I had learnt, and determined to find out a bit more about the church. It has not had an entirely easy relationship with money. In 2009 a fraud case was brought against Bishop Macedo and other UCKG leaders in Brazil after a 10-year investigation. The report accused them of laundering money through London and the Cayman Islands, and using church proceeds to buy property, jewellery and cars, although the case was ultimately thrown out. On online messageboards, ex-members report over-pushy recruiters and strange behaviour by pastors. Some in the UK might have heard of the church through the case of Victoria Climbié, in whose death from abuse the church was implicated and subsequently cleared of involvement.

If the Love School Event was the shop front, what was really being sold? On the following Sunday I went to the Rainbow Theatre for a service called the Tithers’ Consecration. Tithing is a core practice of the church, and stipulates that the first 10th of your income should go to the church. “The Lord will look after those who look after His house,” said the preacher, Bishop Celso Junior, a balding man with a fine singing voice who heads the UCKG in the UK. The congregation – about 400 strong, and almost all black – went up to the front to pay their tithes into red velvet sacks. Then we were invited to hold our wallets in the air for a blessing. A man in the aisle next to me audibly prayed for more money.

Later, “gifts” were invited – a second round of donations. Bishop Celso was clear that the church needed money to fund its expansion. A leaflet about tithing warned against critical “rumours coming from the world and the media”. It wasn’t the only defensive-sounding material. On the “testimonies” part of the UCKG website, where members share transformational stories, comes the disclaimer: “The UCKG HelpCentre is not allowed, by law, to claim that it has a cure for major illnesses.”

Perfect fit: Talshan and Milenna Thompson. Photograph: Tracy Howl

None of which means the UCKG does not do good work, providing hope and community to those who do not otherwise have it. The members I met were friendly and helpful. The UCKG has charitable status, receiving Gift Aid subsidies, and was cleared by an investigation into its fundraising practices earlier this year. There was something incongruous about the mainly South American preachers holding the red-velvet sacks open as the crowd shuffled forward with their envelopes. But perhaps I was being overly sensitive. After all, tens of thousands of people attend these newer churches – which often originate from Africa as well as South America – every week. They are a thriving and competitive market.

“A lot of these neo-Pentecostal churches attract new immigrant communities. I suppose at a crude level what these churches do can seem like exploitation,” says Dr William Ackah, lecturer in community and voluntary sector studies at Birkbeck College. “But on another it’s something that a lot of people follow and believe in. We can take a more sceptical view of the money side of things, but when you meet the people who are members of these churches, they’re much more relaxed about that side of things. They believe in the blessings, and that it has a positive impact on their lives.

“I also think the rise of these churches speaks to broader issues in relation to multicultural Britain. There is a lack of spaces for minorities – they’re not in the BBC or the National Theatre – so these alternative spaces crop up that are not subject to the same kind of scrutiny. These churches can become a home away from home, where people can meet other minorities and migrants. They become a source of information about how to survive in the city.”

The gap between rich and poor in Britain has rarely been so stark, and these churches are focal points of a world that is often hidden from cynical secular journalists. It’s noticeable that the UCKG HelpCentres are found in historically deprived areas – Brixton, Stratford, Kilburn – that are also being rapidly gentrified. But nobody is forced to attend these services, or to give money. The UCKG, and other churches like it, have succeeded by selling hope to the hopeless, by being – in Ackah’s phrase – “spiritual entrepreneurs”. If we disapprove of their methods or suspect foul play, it is incumbent on us as a society to investigate or provide alternatives. I learnt plenty from the Love School, just not much about love.