THAT fateful Saturday night Heidi read an Agatha Christie thriller before falling asleep. She had always dreamed of living on her own in London and had moved into her rented Shepherd’s Bush flat just the day before. It was on the ground floor but had good security. Yet she awoke at 2am with a strange man standing by her bed. It was the start of a three-hour ordeal.

Heidi is good-looking, her face expressive. She speaks seamlessly and with remarkable self-possession, her constant smoking being the only indication of her nervousness. Yet this composed young professional woman now lives in fear because her assailants, who terrorised her in her own home, have not yet been caught.

That night, on Saturday 3 July, the apartment upstairs was empty and her neighbours were having a noisy party.

Suddenly she awoke. In the darkness she made out a man standing in her bedroom. ‘I screamed like an animal,’ says Heidi, a 25-year-old fashion publicist.

Her intruder was startled. ‘Stop screaming or I’ll kill you,’ he shouted. ‘Put a blanket over your head.

‘I’m going to knock you unconscious. But I won’t rape you,’ he went on. ‘I’ve come to teach you a lesson not to leave the windows open.’ She had left the tiny top bathroom window ajar.

At first Heidi thought she was dreaming. She pulled the blanket over her head (she was wearing a short nightdress) and wondered whether he had a gun. ‘I kept telling myself not to panic and do as he said, so he wouldn’t kill me.’

Her assailant asked why she wasn’t at the party, blindfolded her with a T-shirt and the blanket, and pushed her through the flat to the bathroom, where he wiped off his fingerprints.

‘You have a wonderful body. If I saw you on the street I’d chat you up,’ he said. She could feel him kissing her through the T-shirt. ‘But I’m not here to rape you.’

He pushed her back to the bed. She breathed heavily, trying to stop herself breaking down. He told her to ‘shut up’. Then he took her purse. ‘There’s only £25,’ he said, ‘I should have gone to Knightsbridge.’ Heidi was shaking, terrified. ‘He kept threatening to kill me. But I kept making conversation to make things easier. I felt I had to be truthful with him.’

Her head covered, she led him to her hidden antique ring and bank cash card. She was relieved when he asked for the PIN number, thinking that meant he was going, and gave him the wrong number.

‘It’s all right,’ he said, chillingly. ‘My mate outside will check it.’ Heidi was horrified. Suddenly both men were standing in her bedroom. With astonishing presence of mind, she played for time; she told the second criminal to go to the (distant) Kings Street cash machine.

‘Take a cab back,’ her first assailant ordered his accomplice, handing him Heidi’s money. Then he left.

Heidi sensed the man drop his guard. She grabbed her can of CS tear gas, hidden by her bedside. ‘I knew if he saw me, he’d kill me.’ Suddenly she smelt him standing near her, and sprayed the gas where she guessed he stood. He swore madly.

But the gas was five years old and didn’t work properly. ‘I couldn’t believe it. He should have been lying on the floor.’

The man screamed at her. ‘You fucking bitch. I trusted you and what did you do? Now you deserve to be raped and I am going to kill you.’ Heidi punched and kicked. The man was holding her by the wrists and in the struggle bit a chunk out of her arm.

Then he took a kitchen knife, held it to her neck and, to Heidi’s horror, started to molest her. ‘I thought, ‘Don’t think about it. Block it completely. Don’t feel anything. There’s nothing you can do.’ ‘I kept thinking, ‘This is how people feel when they’re being raped’.’ The knife blade was still sticking into her while he assaulted her. ‘‘Wibble’ your hips,’ he repeated, curiously.

Suddenly the accomplice returned, furious that he’d been given the wrong PIN number. ‘I don’t think he wanted his mate to know what he was doing to me. I gave him another wrong number and he left again.’ (She had £500 in her account, but he never withdrew any money.) Heidi was once again alone with her abuser. He now threatened to tie her up and lock her in a cupboard. (He said he’d then call the police.) ‘I didn’t have any rope. I told him to lock me in my cellar. I was afraid of cellars when I was a kid.’

He pushed her to the cellar, with the shirt over her head. ‘He kept marking places on my back with the knife, saying ‘This is your heart and here’s your liver’,’ she says, in astonishingly measured manner. ‘My legs turned to stone.’

Her body was exposed. ‘It didn’t really matter any more what I looked like. I thought, ‘Just kill me. Let my mind have peace. Free me from this.’ He sprayed tear gas on her gaping wound. ‘Thank God it was empty.’ Then he imprisoned her in the cellar, alone and petrified. She listened for sounds from upstairs. Then in a box in the cellar she found two kitchen knives. She didn’t know whether the villains had gone. ‘I thought now I’ll kill them.’

She threw her body against the door, but it didn’t yield. Then she found a garden spade and smashed at it. Finally she crawled through. ‘I don’t know how. The hole was tiny, just 12 inches across.’

Intrepidly, Heidi went through the flat, brandishing her knives. When she found it was empty, this extraordinarily self-possessed woman sat down and smoked a cigarette.

Heidi is German, has only lived in England for 18 months and couldn’t remember the number for the emergency services. ‘I rang 192 and broke down.’ When the police arrived she cried uncontrollably.

They took her to the Brentford Rape Suite – ‘They apologised that it was a male doctor, but I didn’t mind’ – where she underwent forensic tests and gave her 18-page statement.

‘It’s very strange but I didn’t feel dirty. It didn’t occur to me until 12 hours later to take a shower.’

Today Heidi wears jeans, chic green jacket and bohemian jewellery. University educated and smart, Heidi is lively, open and optimistic. The police say she becomes daily more lighthearted and friendly. She had never before been the victim of even petty crime and her experience has had a profound effect on her. (She had the CS gas, which is legal on the Continent, simply because she felt ‘more secure’ with it.) Her assailants had seen photographs of her on the walls of her flat. ‘I feel really frightened in the street if a black man approaches me. Scared he’ll recognise me.’ She has altered her appearance, but not radically. ‘I refuse to change my life completely.’

She has also changed her behaviour. ‘I used to ride my bike in the middle of the night in Brixton, going from one party to another. Now I always take taxis.’

And she has moved. ‘I’ll never dare live alone again. I’ll have a panic button fixed wherever I live. I don’t care what it costs.’ But she doesn’t feel compelled to return to her homeland. ‘This could have happened anywhere.’

She hasn’t ‘yet’ had counselling. ‘I hope it won’t affect my attitude to men. I don’t think it will.’ Her mother is a teacher and her father died when she was an infant. But her sister, an actress, flew to England and helped her to relive the experience while doing cathartic breathing exercises. ‘She made me imagine he was there again.’

Now she says: ‘I feel like skinning those men alive. ‘The worst part wasn’t the sexual side. It was the feeling that this guy could decide whether I should live or die.

‘How easily someone can snip your life.’

Can you help trap the attackers who dropped a key and stole a ruby ring? THE CRIME took place at 8 Leysfield Road, Shepherds Bush, between 2am and 5am on Sunday 4 July. Police are also interested in anyone using the Midland bank cash machine in Kings Street W6 at that time.

Of the two male attackers, one is definitely black. One is 5ft 10in tall, of medium build with broad shoulders and had short afro hair. He was wearing a white T-shirt, with numbers or writing and black vertical stripes, with blue jeans and a belt with large buckle.