Charles Saatchi has told a court he has "no proof" his ex-wife Nigella Lawson ever took drugs - despite an email he sent claiming she was "off her head".
He was giving evidence at the trial of the couple's assistants Francesca and Elisabetta Grillo who deny fraudulently using their employers' credit cards.
The Grillos' defence has claimed the sisters were allowed to spend by Ms Lawson to cover her use of drugs.
Addressing the Grillos' defence counsel Mr Saatchi said: "I have no proof."
Art dealer Mr Saatchi told defence barrister Anthony Metzer QC at Isleworth Crown Court: "I have never, never seen any evidence of Nigella taking any drug whatsoever."
'Severe cocaine habit'
The Grillo sisters, Francesca, 35, and Elisabetta, 41, are accused of using credit cards loaned to them by the couple to spend more than £685,000 on themselves.
Earlier, Mr Saatchi told the court he was "utterly bereft" that a private email he sent to Ms Lawson referring to her being "off her head" on drugs had been made public.
Questioned about the email by prosecutor Jane Carpenter, Mr Saatchi said: "I'm utterly bereft that this private email to Nigella has come back to haunt us both. That's all I have to say.
"The stories that the Grillos were parading was that Nigella had a severe cocaine habit that stretched back a very long time for the entirety of our marriage.
"What I was speculating here was that the Grillos would use this as a defence."
Upon being asked about the drug-taking allegations, Mr Saatchi told the court: "It was hearsay. I personally have absolutely no knowledge that Nigella has ever taken a drug, ever."
Mr Saatchi said he rejected the suggestion his former wife's mind was so "addled" by drugs that she was not aware what she had or had not permitted the sisters to buy.
"Are you asking me whether I think that Nigella truly was off her head?" he asked.
"Not for a second. Over this whole period she was writing books very successfully and appearing on television shows very successfully."
When questioned if he believed the claims, Mr Saatchi went on: "I may have believed it but I may have been completely wrong and they may have been deluded."
He said he was "utterly heartbroken at having lost Nigella" and when asked if he had adored Ms Lawson during their marriage, he said: "I adore Nigella now."
Mr Saatchi and Ms Lawson broke up in the summer after pictures were published showing the millionaire art dealer holding his wife by the throat at the restaurant in Mayfair. They divorced soon after.
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 Saatchi agreed he was "shocked".
Referring again to the incident outside Scott's, Mr Saatchi said: "I was not gripping, strangling or throttling her. I was holding her head by the neck to make her focus, can we be clear?
"Was it about her drug use? No."
Mr Saatchi said Ms 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.
He 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 sisters they could pay back the money they owed and live rent-free in a house in Battersea that Ms Lawson used for filming, but he told the court his then-wife did not agree.
"She was very cross with me," he told jurors.
The art dealer said Ms Lawson told him: "You have to hand this matter straight over to the police."
Mr Saatchi said he thought Francesca Grillo saw his Battersea idea as "humiliating".
He told the court she said: "I'd rather go to jail than go to Battersea," and then said "see you around".
Mr Saatchi told the court the Grillo sisters were originally employed by Ms Lawson as nannies during her marriage to her late husband, John Diamond.
They later looked after his daughter Phoebe, now 19, when she was a child but Mr Saatchi said their role changed as the children got older.
"The children adored them and Nigella was very fond of them and I was very fond of them, and we didn't want them to go so they stayed on as housekeepers and general assistants," he said.
The trial continues.