Celebrity chef Nigella Lawson used cocaine during two periods of her life, she admitted Wednesday as she testified in the fraud trial of two former personal assistants in a London court, reports CNN's Erin MgLaughlin.

She told the court she had used the drug about six times with her late husband, John Diamond, when he learned that his cancer was terminal, in order to give him "some escape from his treatment."

She also used cocaine once in July 2010 when she felt subject to "terrorism" by her then-husband Charles Saatchi, she said.

At that point she felt trapped, isolated and unhappy, she said, and a friend offered her the drug.

But, Lawson said, "I've never been a drug addict, I've never been an habitual user. ... I did not have a drug problem, I had a life problem."

Saatchi had claimed in an e-mail that Lawson had used drugs regularly, but in testimony Friday he backed off that claim.

Lawson's admission of cocaine use came after she earlier testified that Saatchi had threatened to "destroy" her if she did not "clear his name."

She had been asked about her reluctance to attend court as a witness in the assistants' trial - a case that has gripped the media as claims emerge about the couple's troubled personal life.

"I have been put on trial here where I am called to answer, and glad to answer the allegations, and the world's press, and it comes after a long summer of bullying and abuse," Lawson said. "I find it's another chapter in that."

Referring to Saatchi's request for her to attend the trial, made in a letter sent by his lawyers, Lawson said: "He had said to me if I didn't get back to him and clear his name he would destroy me."

Lawson said she felt she had to do her civic duty. "It's difficult for me, it's very difficult for my children, but I want to do the right thing," she added.

The former aides, Italian sisters Francesca and Elisabetta Grillo, deny embezzling hundreds of thousands of pounds on company credit cards while employed by Lawson and Saatchi.