Ms Castberg, a Danish-born British citizen, was hired as director of Copenhagen's Arken Museum of Modern Art on the basis of her impressive qualifications. After three years, they have come back to haunt her and the museum, the B.T. newspaper reported yesterday.
Last month, the mysterious, glamorous woman - newspapers say she is like Meryl Streep - was dismissed by Copenhagen County, which said she was a poor manager. The county gave her 600,000 kroner (about pounds 65,000) in severance pay.
Now the museum board wants proof of her claims that she was educated at the Sorbonne and the Courtauld Institute of Art in London, was a columnist for the Paris-based International Herald Tribune in the Seventies and worked at two Czech museums.
None of those places had heard of her, said Danish newspapers, which have been investigating her past since her dismissal on 20 August.
The mystery deepened when Ms Castberg, 48, vanished, saying that she would collect proof of her claims. Her lawyer, Per Magid, said he no longer represented her.
If she returns, the museum and county may sue unless she proves she was worthy of the job and the "golden handshake". A county spokesman said that employment had to be based on trust.
One tabloid said she was so "beautiful, charming and intelligent" that the male-dominated hiring committee might have not have been looking at her curriculum vitae.Reuse content