London (CNN) -- 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.
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.
'No hard evidence'
In his testimony last Friday, Saatchi addressed the claim made in an e-mail he sent to Lawson in October that alleged she had used drugs.
He told the court he never saw his wife taking drugs during their 10-year marriage and he had no hard evidence she had done so. He also said he was "utterly heartbroken" by the end of their relationship.
In the e-mail, which was shared with the court by the defense in a pretrial hearing, Saatchi wrote that the assistants would likely "get off" because Lawson was using cocaine and marijuana on a daily basis and "allowed the sisters to spend whatever they liked."
The allegations emerged in June, around the time the couple were photographed in a restaurant having an argument.
In the photos, which were splashed across the front pages of national newspapers, Saatchi is seen with his hand around Lawson's throat. Saatchi accepted a police caution for assault, and the couple announced they would divorce soon afterward.
'She was a rock'
The two defendants, who worked for Lawson and Saatchi for a number of years, were supposed to use the cards for household expenses, but allegedly spent large amounts on themselves.
Lawson acknowledged Wednesday she wasn't familiar with every detail of the purchases made by the Grillo sisters.
She told the court she had employed Elisabetta, also known as Lisa, while her ex-husband had hired Francesca.
"I loved Lisa. She came to me in a difficult time in my life. She was a rock," Lawson said.
She said Elisabetta Grillo had left her job for a while, and when she came back she'd been increasingly bitter and unhappy.
"I do not think her bitterness was towards me personally. I think it was towards her life," the chef said.
Lawson ignored the crowd of reporters and photographers waiting outside Isleworth Crown Court as she entered earlier, wearing black and looking somber.
Transactions top $1 million
Saatchi's accountant gave details of the sisters' alleged spending on luxury goods in court last week, including purchases from Prada, Miu Miu and Louis Vuitton.
The prosecution also showed Saatchi a list of the top 50 transactions made by the sisters, totaling more than $1 million, which he said he did not recognize and had not authorized.
He did not know whether Lawson had approved them, he said.
Lawson, whose culinary skills and flirtatious manner have long entranced UK audiences, has also appeared as a judge on ABC show "The Taste" in the United States. A second season of the show is due to air in January.