It seems insane. Giving up everything you have to go to one of the most dangerous places in the world to show Jesus' love to criminals, prostitutes and drug addicts. You might at a pinch go for six months or a couple of years. But how about going for the rest of your life?

This is what Jackie Pullinger did.

Jackie Pullinger began to make this huge decision early. As a young girl at Sunday School she decided she wanted to be a missionary - and that was before she really knew what a missionary was. But as she grew up, she forgot about her childhood ambition for a while and became a student at the Royal College of Music.

It was only when she started meeting regularly with other Christians in a friend's home that she thought about being a missionary again. Then one night, she had a dream.

"I saw a vision of a woman holding her arms out beseechingly as on a refugee poster. I wondered what she wanted - she looked desperate for something… Then words moved past like a television credit: WHAT CAN YOU GIVE US?"

After a series of dreams and vivid experiences, Jackie decided she would go to Hong Kong. The trouble was, no one else agreed with her.

She applied to every missionary group she could think of, and also to church organisations and the Hong Kong government - but all the doors closed in her face. You're too young, you're too inexperienced, you have the wrong qualifications, she was told.

She was about to give up, when the vicar of a church she helped in told her, against the received wisdom of everything else she had heard, to go to Hong Kong anyway.

In 1966, Jackie Pullinger gathered up all the money she had and bought a passage on the cheapest boat to Hong Kong she could find. She only had enough money for a one-way ticket, so there was no turning back.

She almost didn't make it past Hong Kong immigration. But she was eventually allowed in and found a job teaching at a primary school in the Walled City. This was an area where the Hong Kong police had no regular jurisdiction. As a result, it was Hong Kong's most deprived and dangerous area.

Next: Triads, dragons... and faith