TV chef Nigella Lawson arrives at Isleworth Crown Court in west London December 4, 2013.[Photo/Agencies]

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"I felt this would not become a fraud case and I would be put on trial and that is what happened," she said. "But I'm glad to answer the allegations here and to the world's press," she added.

Lawson told the jury that following the "awful incident" at the restaurant in June, false allegations of her drug use began circulating on what she called a PR blog.

Those allegations, she said, had been "dedicated to salvaging Mr. Saatchi's reputation and destroying mine".

She told the court her reluctance to give evidence in the trial had angered Saatchi. "He had said to me if I didn't get back to him and clear his name, he would destroy me," she added.

The court had previously heard that Saatchi wrote her an email in October in which he said the two assistants on trial, Italian sisters Elisabetta and Francesca Grillo, would be able to beat the fraud charge because of her drug use.

"I can only laugh at your sorry depravity," he said in the email, which was read in court. "Of course now the Grillos will get off on the basis that you ... were so off your head on drugs that you allowed the sisters to spend whatever they liked."

In court last week, however, Saatchi said he had no proof that his ex-wife had ever taken drugs. "Are you asking me whether I think that Nigella truly was off her head? Not for a second," he said.

The court has been told by the prosecution that in the four months to June 2012 alone, Francesca Grillo, 35, spent an average of 48,000 pounds per month and 41-year-old Elisabetta 28,000 pounds.

At various times during the four years to which the charges relate, the court has heard, the sisters spent lavishly on flights to New York, hotel stays, designer handbags and clothes.

Lawson told the court Elisabetta was a stalwart who had helped her through the death of Diamond. She said the fraud allegations "broke our heart" when revealed to her and Saatchi.

The trial continues.