Hea Woo (not her real name) sits across the table in the basement restaurant of a Premier Inn hotel in central London.

It seems a strangely ordinary place to hear a remarkable life story. 

A North Korean escapee, Woo was one of as many as 200,000 people held in labour camps across the secretive state. Unlike many others, she survived her sentence and later escaped into South Korea.

After trying to flee North Korea into China – an act Pyongyang considers illegal – Woo was moved between 10 different prisons. She describes the conditions as a 'living hell'. Many others are too traumatised to speak about it at all.

'When people died the guards just broke the dead bodies in to two pieces, put them in a cart and took them outside,' she tells Christian Today in an interview. 

'Once in a while we had to take the bodies outside of the camps to cremate the bodies. But the crematorium was so small and there were so many dead bodies that we had to cut the dead bodies into small pieces with an axe,' she adds.

'After the cremation the ashes were scattered in the fields but often they were blown away in the wind. So the inmates had to walk over the ash. I thought; "One day the prisoners will walk over me".'

Already suffering from malnutrition when she arrived, Woo describes how she shared a cell designed for 50 with 200 other inmates.

'We were so cramped if you got up in the middle of the night to go to the toilet you couldn't find any space to squeeze back in to sleep. There wasn't even space to stand properly,' she says.

'In one corner of the cell there was a toilet but to prevent the prisoners from escaping there were no windows in the toilet – only a hole in the floor,' she adds.

'So it was really disgusting and the smell was so horrible. The people suffered headaches because of the smell and often we would get sick. Also there were lots of rats in the toilets.'

Woo's husband died in a similar labour camp after being arrested for his Christian faith.

Open Doors, a Christian persecution charity, ranks North Korea as the worst country in the world to be a Christian.

'Persecution is led by the state which sees Christians as hostile elements that have to be eradicated,' the charity says.

After converting to Christianity herself before being imprisoned, Woo says: 'In that horrid situation God was there too.

'I started to pray for the lost souls there who are dying without knowing Jesus Christ. I prayed to the Lord saying: "I want to be a salt and light in this place for these poor souls".'

She was caught speaking about her faith on four separate occasions and tortured each time. On one particularly brutal occasion she says she was tortured for three days in a row.

'I wasn't scared of the torture but I was scared that I might lose consciousness and in my unconsciousness I might deny Jesus' name. That was what I was scared of.

'But on the fourth day I just collapsed and felt I couldn't stand any more. So again I cried out to the Lord and I was reminded of the verse from Jeremiah 33.3: "Call to me I will answer you and I will show you unimaginable things..."

'So I was able to bear all the sufferings at the time. I was taken back to my cell and heard the really loud, audible voice of the Lord. It said: "My beloved daughter, you walked on water today."

'It was a really loud strong audible voice but no one else heard.

'I realised that the Lord was there when I was tortured. I had to really thank him that he was there with me. After that day I didn't get tortured. The Lord protected me.'

Speaking through a translator, Woo is understated. She describes her treatment at length but without emotion. Until, that is, she comes to her escape, when the tears begin to flow.

After being released from prison she returned again to the Yalu River which separates North Korea from its only ally, China.

'When I stepped into the river the rain changed into snow which veiled the guards,' she says. 'But because it was rainy season there was a very strong current. One moment I just was swept away in that current and lost my consciousness.

'But when I opened my eyes I was on the other side of the river, in China!

'On the bank there was a very high electric fence. So I prayed at that time that "Lord, you have led me this far. If it is time for me to go to you, then just take my life." Then I put my hand into the fence.

'But after a while I thought I was dead but I was able to open my eyes...I realised there was no electricity.'

Starting to cry she goes on: 'The journey from that point up to the border between China and Myanmar was not easy either. We were stopped several times and each time we were taken to the police station. But strangely, amazingly, I wasn't searched or asked to show my ID.

'So all those times I was able to go through the border from China to Myanmar. From Myanmar to Thailand we had to get a boat for about six hours.

'On that boat I suddenly realised nobody would arrest me even if I sang out loud praising the Lord. So for all that six hours I praised the Lord with a strong voice!

'So I really thank the Lord he answered all my prayers, whether it was a prayer in a whisper, or a prayer in a shout. All my prayers have been answered! My confession of faith is in Psalm 119.71 which says: "It is for my good that I have been afflicted so that I can follow his law."

'Now I am the happiest person in the whole world! I have nothing but because of Jesus Christ in me I am so happy!'

To find out more about Open Doors' work in North Korea click here.