In an exclusive 20-minute interview with the state-owned ORF channel, Natascha Kampusch is expected to reveal further details of her eightyear ordeal at the hands of the obsessive loner who made her his slave, and to address some of the details of her story which, 11 days after her escape, remains vague and contradictory.

Disturbing questions are now being raised about her family life before the abduction, about the ordeal itself, and about the degree of control exerted over her by the team of social workers, psychiatrists and government officials now treating her.

Since her escape, Natascha has had one brief meeting with her parents, Ludwig Koch and Brigitta Sirny, but reports suggest it was not the joyous reunion that might have been expected, and a second meeting was cancelled at the last moment. Said Walter Poechhacer, a private detective who wrote a book about the case:

"Something must have happened in that family. Something that had to be hidden. When the child begins to speak there will be surprises."

Both parents now attest to an unfaltering devotion to their daughter, although her father is now charging reporters 1,500 per interview. It has also emerged that, following her disappearance in 1988, investigators briefly probed allegations that she may have suffered sexual abuse in her own family. There is no suggestion the rumours were true, but the revelation has fuelled speculation surrounding Natascha's apparent reluctance to be reconciled with her family.

Before her disappearance, Natascha's last conversation with her mother ended in a row and a slap across the face. At the time, Natascha was an overweight 10-year-old who was bullied at school. Following her parent's acrimonious separation, she had gained more than a stone-and-ahalf in just over a year.

After the separation, Natascha lived with her mother on a grimy housing estate. There she caught the attention of the 36-year-old handyman, Wolfgang Priklopil. On the morning on 2 March 1998, Priklopil bundled Natascha into a white Mercedes van and drove her to his suburban house and the underground cell which was to become her home for eight years.

Psychologists have drawn a profile of Priklopil as a man obsessed with control, who used a system of rewards and punishment to dominate Natascha. But the true nature of their relationship may have been more complicated. She has refused to answer "intimate questions" about her relationship with the man she came to call "Wolfi". Forensic tests have confirmed she did enter Priklopil's bed, but investigators have not yet found any conclusive evidence that their relationship was sexual.

After Natascha escaped on 23 August, Priklopil committed suicide by throwing himself under a train.

Detectives were allowed to question the 18-year-old in three 20-minute sessions last week, but they said many "burning questions" about the case remain unanswered. Meanwhile, bidding for her first newspaper interview is said to have reached 500,000.

Her father, Ludwig Koch, has filed a claim against Priklopil's estate as compensation for her suffering.

Natascha has spent the days since her escape cocooned in a sanatorium outside Vienna. Psychologists say she has been trawling the internet in an attempt to catch up with some of what she has missed.