Celebrity chef Nigella Lawson's former husband Charles Saatchi has finally given an explanation as to why he grabbed her by the throat at a Mayfair restaurant, a story that made headlines around the world.

"I was not gripping, strangling or throttling her. I was holding her head by the neck to make her focus," he told Isleworth Crown Court on Friday.

Saatchi filed for divorce from his wife of 10 years after she failed to defend him in public following the publication of pictures that appeared to show him grabbing her by the throat.

"I am sorry to announce that Nigella Lawson and I are getting divorced. This is heartbreaking for both of us as our love was very deep, but in the last year, we have become estranged and drifted apart," Saatchi told The Mail.

Saatchi has been widely criticised over the alleged choking incident. Shortly after the pictures were published, Lawson was pictured with her son Bruno leaving her marital home with a suitcase.

Following their divorce a few months back, the case has been ruffled up with new claims by Saatchi that Lawson takes drugs and that she trashed her daughter's life.

Italian sisters Francesca and Elisabetta Grillo, who were Lawson's assistants, are on trial for committing fraud while they worked for the couple. They allegedly blew £300,000 on taxis, flights and clothes.

"The defendants' case is that Ms Lawson lied to her ex-husband about her drug use and the expenditure incurred by the defendants. This was because she was fearful about Mr Saatchi's reaction if he knew about the extent of the drug use. Therefore there was a culture of secrecy in their marriage," Anthony Metzer QC, who is defending Elisabetta Grillo, said.

Lawson was aware that the defendants knew she was a habitual drug user, so she allowed this expenditure, Metzer added.

"The story that the Grillos were raising was that Nigella had a severe cocaine habit that stretched back a very long time, the entirety of our marriage, and that she took cannabis and shared it with her daughter for a very long time," Saatchi added.