When I was teaching mathematics at Winchester College or at theological college, the idea of deliverance, and indeed of the Devil, seemed distinctly medieval.

For me, it all changed on a July evening in 1975, when a couple arrived on the doorstep to complain about the social services. A few minutes later the woman calmly announced that she was in league with the Devil. When I suggested that she renounced the Devil, she screamed across the room that she renounced God and started to talk in the voice of an old man. A tense evening ensued. Eventually, Michael and Rosemary Green, my rector and his wife, arrived. After much prayer some calm was restored. The medical profession said that she had an incurable personality disorder; the diocesan exorcist anointed her with oil and she leapt in the air complaining that the oil was burning her. A saintly cleric took her into his house and prepared her for baptism the following Easter. She now leads a reasonably normal life – with some discernment of other people's spiritual problems.

This was the beginning of many encounters. After some 40 years of ministry, I am still amazed how calm prayer can bring order out of chaos and how similar the symptoms of demonic interference are all over the world.

Of course, most of the problems are dealt with very gently and without any spiritual fireworks. In England, there are more requests for help with troubled buildings – factory, office, pubs as well as houses. The results are encouraging. People are grateful to be taken seriously and even more grateful when their problems cease. A businessman with ME for seven years who has been cursed is back in the gym – with a suitably impressed GP who had been bemused by his problem. A person who had somehow acquired 'demonic' tongues and who ended up slithering across my study floor is now ordained and helps many others with similar problems.

A publican, with a highwayman allegedly buried under his bar, is duly grateful when his children's nightmares disappear and his son's eczema is healed through the prayers of the parish team. A factory manager with a distraught work force (girders crashing, strange footsteps, electrical failures everywhere, a door controlled by a keypad opening with no one present...) is extremely grateful. A troubled owner of horses which won't settle in her stables is relieved when after prayer and a douche of consecrated water a force leaves the stables and virtually knocks over my fellow worker. The somewhat rebellious daughter of a Wycliffe Bible translator, living in a Christian centre in PNG, says that she has been visited by spirits in her bedroom for 10 years. After prayer, her bedroom calms down. Soon afterwards, she professes conversion and is baptised.

In Tanzania, where my daughter Katy and her son in law run Neema Crafts ( a project which employs 100 severely disabled people) it was wonderful to reconnect with Paulina. In 2015, she had complained of severe stomach pain, sickness and dizziness. The African chaplain, my son in law, another leader and I prayed with her. She associated her illness with a Masai curse. We prayed to break its effect. She has remained really well ever since and now takes on increasing responsibility in the project.

These sorts of experience caused me to respond when The Times ran an article, 'The Devil Goes Missing', about the proposed exclusion of the Devil from the Baptism service. I wrote a long letter. The result was a full page article one Saturday.

I believe the Church of England is far too reticent about this important ministry. If we don't clearly offer help, people turn to spiritualists often paying large sums (one family I helped had paid £500 and their house became so bad that they had to move out). This ministry, conducted under proper episcopal authority and with due caution, is a marvellous witness to the truth of the Resurrection of Jesus. How can prayers, in the name of Jesus, cleanse a room unless Christ is truly risen? When, in rural Africa, a seemingly demonised woman speaks to you in Oxbridge English saying 'Go away, I'm not leaving this person' as a mathematician I see no natural explanation and a confirmation of the truth of the stories in Mark.

My book begins with some theological considerations – most notably that it is, I contend, almost impossible to have a doctrine of God which does not include some spiritual opposition. Then I have looked at various pastoral situations including areas where mistakes are often made. Finally, I have looked at the history of the deliverance ministry and its importance in the early church and various missionary situations as well as at home.

John Woolmer was ordained in 1970 and was Rector of Shepton Mallet for 20 years and has led many overseas missions.

'The Devil Goes Missing?' is published by Monarch, price £14.99.