Image copyright Thinkstock

There are evangelical Christians who believe that medical miracles are a reality, writes Jolyon Jenkins.

"Can I put my hand on your face?", asks Alun Leppitt.

Alun is the pastor of a Pentecostal church in Southampton. He's a burly man who works as a video editor to pay the bills, but his passion is curing people through the power of prayer. I don't have much wrong with me apart from a nagging mouth ulcer, but he's willing to give it a go.

"We command this mouth ulcer to go, in the name of Jesus," he says, palm on my cheek. "We command any pain, infection or trauma to go."

Find out more Image caption Donna and Alun Leppitt Listen to Out of the Ordinary: The Power of Prayer, featuring Alun and Donna Leppitt, on BBC Radio 4, Monday 10 March at 11:00 GMT Or catch up on iPlayer

I don't like to disappoint Alun, but I can't feel any difference. He has two more attempts but there's no change.

But mouth ulcers are small beer for him, and he's not interested in small psychosomatic effects. He and his wife Donna tell me of a woman who had a child despite having had a hysterectomy - of people with advanced cancer who suddenly become well after prayer.

From another healer, Ian Andrew in Somerset, I heard of a woman who got a new heart as a result of prayer.

"Literally, a new heart?"

"Yes."

"What happened to the old one?"

"It was replaced."

These claims are, by any standards, implausible. But in the world of Pentecostal healing, no-one worries about that. In fact, the more impossible the miracle (and they use the term without embarrassment) the better, because it's more effective for spreading their message.

Alun and Donna Leppitt are the UK end of a worldwide fellowship of evangelical Christians called Global Awakening. In countries like Mozambique and Brazil, Global Awakening missionaries are converting people to Christianity with spectacular displays that claim to heal through prayer. They say they cure blindness and deafness in big open air meetings.

Image copyright Science Photo Library

There have been attempts to measure the effect of prayer. An American professor of religious studies, Candy Gunther Brown, did research in Mozambique. Using portable audiometer equipment, she found a difference between the ability to hear before and after the prayers. The results were published in the peer-reviewed Southern Medical Journal. Whether the improvements lasted is unclear, because the villagers mostly disappeared into night after the prayer session. It could all just be a placebo effect - the power of suggestion rather than prayer.

If you wanted to test whether prayer on its own can cure, without the power of suggestion, you need to ensure that the people being prayed for don't know it. In 1988, Randolph Byrd did an experiment with heart patients in San Francisco General Hospital. One group was prayed for, and the other wasn't. The prayed-for group did better. But critics suggested the results could have been achieved by chance, and were sceptical about the methodology.

Miraculous healings Image copyright Thinkstock The process of making someone a saint is called canonisation. In the Catholic Church, at least two miracles must be attributed to would-be saints for the Vatican to proceed with canonisation. In 1986, atheist haematologist Jacalyn Duffin was asked to analyse some bone marrow samples of a patient with aggressive leukaemia. She thought the patient had died and her expertise was being used to file a lawsuit against a doctor or hospital. She had no idea her investigations would assist the Vatican in creating the first Canadian-born saint. Read Prof Duffin's story

When, in another study, a group of heart patients were told they were being prayed for, they did worse - presumably because they worried that, if God was being enlisted, things must be really bad.

Another study in the Journal of Reproductive Medicine seemed to show that women receiving fertility treatment were more likely to conceive if they were prayed for. It was a remarkable result, but then it turned out that one of the three authors of the paper denied having had anything to do with the experiment, and another one was revealed as a parapsychologist who was jailed for financial fraud. The paper was taken off the journal's website.

When you get contradictory studies like this, researchers often do a meta-analysis, in which they combine all the studies in an attempt to get a clearer picture. The Cochrane Collaboration is a group of academics specialising in meta-analysis, and a few years ago some of their people took a look at prayer studies. The lead author was Leanne Roberts, who was at the time an administrator with the Cochrane group but was planning to become a vicar and is now canon treasurer of Southwark Cathedral. Roberts found no clear effect of prayer but was not prepared to say it was medically useless.

More from the Magazine Image copyright Getty Images Does religious belief boost sporting performance, asks Matthew Syed. Do prayers help players?

To believers, all this is by the way. They are not interested in little effects that are on the border of statistical significance - they want big flashy miracles. And healing isn't the half of it. Global Awakening members also claim to have had gold teeth miraculously appear in their mouths, to have had enormous and unaccountable gems materialise during prayer sessions and even to have raised the dead.

Tyler Johnson runs a ministry called the Dead Raising Team in the US. He claims to have brought several people back to life. He says he even persuaded the authorities in his state to issue him with an official photocard which lets him through police lines at car accident sites.

Johnson appears in a new documentary film called Deadraisers, which follows enthusiasts as they trail round hospitals and mortuaries trying to bring people back to life. Sadly, those they pray for in the film remain resolutely dead.

Johnson is unwilling to provide successful case studies. And in general, the proof that believers cite is a bit unconvincing - for example, there is an American heart surgeon who allegedly brought a heart attack patient back from the dead with prayer. But he was also using a defibrillator, and other doctors find the story entirely unremarkable.

Image copyright Thinkstock

Alun and Donna have not had any success with dead raising either. Last year, Donna's brother died of a heart attack. By the time they got to the mortuary, he had been dead for eight hours. They prayed over him for nearly an hour, and although at one stage they thought they saw him move, that was as good as it got.

Are they discouraged? "Not at all," says Alun. "Practice makes perfect," adds Donna. "But in this country, we don't often get access to dead bodies."

And it takes a lot to shake Alun and Donna's faith. Alun himself has serious medical problems. He was diagnosed with ulcerative colitis in his 20s, has had complications, major surgery, and is now on a waiting list for an ileostomy. He needs a miracle. But so far, and despite the prayer, none has come.

Follow @BBCNewsMagazine on Twitter and on Facebook