Nigella Lawson has accused her ex-husband Charles Saatchi of trying to destroy her with claims that she was a persistent cocaine user.
In an emotional court appearance, Ms Lawson claimed he threatened her if she didn't go back to him and 'clear his name' following the throat-grabbing incident outside a Mayfair restaurant last year.
And she said she had been put on trial by the 'false' drug-use allegations which came after a summer of 'bullying and abuse'.
She said claims of her drug habit had been circulating on the internet and 'sent to every media outlet'.
Ms Lawson was giving evidence against former aides accused of defrauding her and Mr Saatchi for £685,000.
The couple divorced in July after pictures of Mr Saatchi gripping her throat at Scott's restaurant in Mayfair were published.
Isleworth Crown Court has heard of an email in which Mr Saatchi accused her of being 'so off your head' on drugs that she had allowed her PAs -Italian sisters Francesca and Elizabetta Grillo - of spending as much as the liked on his company credit card.
Ms Lawson told the jury she had not wanted to come to court because 'to say my relationship with him is not good is nowhere near'.
Her refusal angered her ex-husband and, she said: "If I didn't go back and clear his name he would destroy me.
"He had already started spreading false allegations of drug use, in particular that awful incident in Scott's."
However when Mr Saatchi found out that the Grillo sisters would be claiming in court that Ms Lawson had a drug habit he 'menaced her' she said.
"I said, 'What drug allegations? There are not going to be any. These allegations appeared in a PR blog that had been designed to salvage Mr Saatchi's reputation and savage mine which was circulating on the internet," she said.
"They had been sent to every media outlet and I felt this would be said and I would be put on trial."
Ms Lawson added: "That's what happened, I have been put on trial here but I'm glad to answer the allegations here and to the world's press. It comes after a long summer of bullying and I found it another chapter in that.
"I felt I had to do my civic duty. It has been difficult for me and very difficult for my children but I want to do the right thing."
Later, Ms Lawson admitted she had used cocaine but insisted she is not a habitual user of the drug.
She said she had used the drug half a dozen times when her then husband John Diamond was terminally ill and in 2010 when she was subjected to 'intimate terrorism'.
She also admitted smoking cannabis in the last year of her marriage to Mr Saatchi, but said she has now given up.
She said: "I have never been a drug addict. I've never been a habitual user. There are two times in my life when I have used cocaine.
"I have to be honest, I have smoked the odd joint. It's a false friend and not a good idea. "I have to say, since freeing myself from a brilliant but brutal man, I'm now totally cannabis, cocaine, any drug-free."
Ms Lawson said the first instance was with her late husband when he found out his cancer was terminal, and said she had taken it with him on six occasions. The second occasion was when a friend gave the drug to her.
She added: "There was another time I took cocaine. In July 2010 I was having a very, very difficult time.
"I felt subjected to intimate terrorism by Mr Saatchi."
She said claims she was a drug addict were 'absolutely ridiculous'.
She also described what had happened during the much-publicised incident at Scott's restaurant in Mayfair.
She claimed the incident was sparked when she commented on a person walking by with a baby.
She said: "I said 'I'm so looking forward to having grandchildren.
"He grabbed me by the throat and said 'I'm the only person you should be concerned with'."
Ms Lawson, 53, had been called as a witness by the prosecution to give evidence against the Italian sisters accused of a four-year fraud.
They are accused of squandering £685,000 on holidays, air flights and designer clothing charged to Mr Saatchi's company credit card.
Francesca, 35, and Elizabetta Grillo, 41, both of Bayswater, plead not guilty to fraud between 2008 and 2012.
The case continues.