Debs, a heroin addict, was looking for matches to go 'chasing the dragon' when she stumbled on something she had never read before.

It was a Gideon Bible, in the drawer of the flat where she was staying.

High on heroin, she began to read. 'I had never read the Bible before. I just read there that I was in real trouble, that there was a living God to whom I owed an account for my life, this life that I had just trashed.' 

Her story is one of those being told by the Christianity Explored evangelism course, that has just launched in its 100th country, Ivory Coast, and is planning to be in a further 75 countries by 2021.

Debs grew up in an atheist home. 'We never went to Sunday school, never went to church. I lived life on my own terms without any reference to God. I lurched from one disastrous relationship to another, looking for love in all the wrong places.'

When she was 30 she got involved with a younger man who was a heroin addict. 'When I found out he was doing heroin, instead of leaving him I started taking heroin as well.' That was the start of an 18-month ordeal as she tried repeatedly to come off the drug. 'Life just went from bad to worse.'

It was when she was staying in a friend's flat, rummaging around in some drawers looking for matches, that she came across the small Gideon New Testament. 

She realised she couldn't commit suicide. 'Life was living hell, but death meant facing Him. I was too scared to do that. I saw in the Bible that I was in real trouble with a real God. I didn't know who Jesus was but I knew I had to get to a church.'

It was Good Friday. She was at the back of the church, ready to make a quick getaway, when they began reading about the crucifixion from Matthew's Gospel.

'I just sobbed. What I heard was that he had died on the Cross for me. All the things that I had done, and the punishment that was coming my way, he had taken on the Cross.' 'I just knew that I was God's daughter. I was sobbing, just sobbing. I walked out of there knowing that God was my father.'

That was nine years ago.

'God has healed and restored every area that I had single-handedly trashed.' He has helped her settle debt and restored her relationships with family and friends and also her career. 'I can't thank him enough for what He's done for me.'

Christianity Explored, launched 15 years ago, is a seven-week course founded at All Souls Langham Place in London and based on the Gospel of Mark.

It is an informal method of exploring who Jesus is, why he came and what it means to follow him and Debs is just one of tens of thousands have become Christians both in the UK and abroad as a direct result of doing the course.

Ian Roberts, chief executive of Christianity Explored, said, 'Since it was first launched, CE has been the catalyst through which tens of thousands of people, of all ages, classes, races and educational achievements have come to faith – both in the UK and, increasingly, abroad. Reaching that 100th known country is an important milestone and a thrill for us.

'But in reality it's likely to be many more than 100. This is because we regularly discover people benefiting from it – often in some quite obscure places – where we had no idea anyone had access to it.

'CE's prime use has always been as an effective evangelistic method. But we have also found it a vital discipleship tool, for example in places where people readily accept Jesus but lack the scriptural knowledge and understanding to consolidate their heart experience.

'Another hallmark of CE is its proven flexibility. It works just as well in a taught environment as in small group study, in one to one personal evangelism and even in studying it on one's own.'