Charles Saatchi has told a court he was "utterly bereft" that a private email he sent to ex-wife Nigella Lawson referring to her being off her head on drugs has been made public.
The email he wrote to the TV chef was read in full to jurors but, when asked if he believed allegations that Miss Lawson was a habitual cocaine user, the art dealer said: "I do not know."
"If you ask me whether I actually knew whether Nigella ever took drugs, the answer is no," Mr Saatchi added as he gave evidence at Isleworth Crown Court in west London, where his two former personal assistants are on trial accused of fraud.
Italian sisters Elisabetta and Francesca Grillo are accused of using credit cards loaned to them by the celebrity couple to spend more than £685,000 on themselves.
Mr Saatchi listened as the email he sent to Lawson on October 10 was read out to jurors at Isleworth Crown Court in west London.
In it he referred to his ex-wife as 'Higella' at one point.
He wrote: "Nigella, I was sent these by a newspaper and I can only laugh at your sorry depravity.
"Of course now the Grillos will get off on the basis that you ... were so off your heads on drugs that you allowed the sisters to spend whatever they liked and yes I believe every word the Grillos have said, who after all only stole money."
The email went on: "But I'm sure it was all great fun and now everything is perfect - bravo, you have become a celebrity hostess on a global TV game show. And you got the Pass you desired, free to heartily enjoy all the drugs you want, forever. Classy."
Mr Saatchi said Miss Lawson was "very cross" with him when he told her he had confronted their personal assistants about their alleged misuse of his company credit card.
The multi-millionaire, who went through a high-profile divorce from the food writer earlier this year, said he thought the Grillo sisters had been "naughty" but he wanted to put the matter behind them while Ms Lawson wanted to call the police.
Mr Saatchi said he told the pair that they could pay the money they owed off and live rent-free in a house in Battersea, central London, that Lawson used for filming but his then-wife did not agree.
"She was very cross with me," he told jurors.
"And she said 'How could you do that? I would never have them in my house again...'
"And I said 'I'm really sorry. I was trying to cause the least friction possible and didn't want a lot of disruption...
"'Sorry if I misread it'."
Mr Saatchi went on: "She then said 'You have to hand this matter straight over to the police'."
It is alleged that the Grillo sisters lived the "high life", spending the money on designer clothes and handbags from Louis Vuitton, Christian Dior and Vivienne Westwood.
Referring to the atmosphere in the family home before the breakdown of his marriage to Ms Lawson, Mr Saatchi said: "It was a happy home where everyone just buzzed around happily."
He said he was "utterly heartbroken at having lost Nigella" and said he wished this year had never happened.
When asked if he had adored Ms Lawson during their marriage, he said: "I adore Nigella now. I absolutely adore Nigella and I'm broken-hearted to have lost her."
Mr Saatchi said he has no proof of Ms Lawson's alleged drug-taking.
Responding to defence barrister Anthony Metzer QC, he said: "Like you, I like proof. I have no proof."
He later said: "I have never, never seen any evidence of Nigella taking any drug whatsoever.
"I want to be helpful, but I genuinely have no real knowledge at all."
When asked by Mr Metzer if he became aware of Ms Lawson's alleged drug-taking around the time of the "Scott's Restaurant incident", he said it was indeed around that time.
Mr Metzer asked if he was "shocked", to which Mr Saatchi said he was.
"I'm very against drugs," he added.
Mr Metzer then said: "You are a friend of Trinny Woodall who feels very strongly about this issue?"
Mr Saatchi rolled his eyes at this question and said: "Yes."
Earlier, The accountant in charge of Mr Saatchi's finances has told a court he increased his personal assistant's credit limit to £100,000 without telling the art dealer the amount.