By DAVID WILLIAMS and MARCUS OSCARSSON

Last updated at 00:25 11 January 2008

The teachers and pupils thought that the new boy, Adam, was a little strange.

Though quiet and studious, he appeared very scared. And he flat-out refused to take part in sport with the other 13-year-olds.

Yesterday, they discovered that something was indeed amiss - as Adam turned out to be a 33-year-old woman, on the run from police.

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Barbora Skrlova was arrested yesterday after fleeing the city where she had been living her lie for four months.

The bizarre masquerade in Norway was an attempt to escape from an investigation in her home country, the Czech Republic.

The details of that case, according to police, are completely baffling.

The mystery involves an obscure religious sect and allegations of child abuse. Skrlova's role remains unclear, Norwegian police spokesman Sven T Roer said.

"We have not been able to figure out what is up and down in this case," he said.

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Skrlova first came to the attention of authorities in May, when she was found at a house in the Czech Republic during a raid by police investigating child sex abuse.

At that time, she claimed to be a 13-year-old girl called Annika.

The adults involved were said to be members of The Grail Movement, which follows the teachings of a 19th century German mystic.

The organisation, which has its headquarters in Austria, has offices in Britain.

Annika was taken into care but police inquiries soon showed she was in fact Skrlova, whose 75-year-old father is head of the Czech branch of the movement.

She had already escaped, however, allegedly with the help of a couple involved with the sect. They are thought to have used their 13-year-old son Adam's passport to take her to Denmark and then Norway.

As Adam, she enrolled in school in Oslo. Her head was shaved and she bound her breasts.

"Looking back, we can say that we wondered about Adam's behaviour . . . but this is not easy to know," said Ingjerd Eriksen, principal of the Marienlyst school.

"Children at this age are very different and can be masculine or feminine."

A staff member who thought the boy seemed troubled contacted the authorities. But Adam managed to disappear.

A picture was circulated in Norway and he was finally captured in the north of the country - where his true identity was discovered.

"She said she was in Norway because she did not want to be a witness in the criminal case going on in Czech Republic," said Oslo Police Chief Hanne Krisint Rohde.

Skrlova, who arrived at Prague airport yesterday holding a teddy bear and a children's book, is said to be in a "shattered" state.