London ( CNN ) -- Charles Saatchi , the millionaire ex-husband of celebrity chef Nigella Lawson , said Friday he believed his ex-wife had taken drugs but had no evidence of it , as he testified at the trial of two former assistants accused of fraud . The former assistants , Italian sisters Francesca and Elisabetta Grillo , deny embezzling hundreds of thousands of pounds on company credit cards . Allegations of drug use by Lawson were made in a pre-trial hearing for the case earlier this week , when an e-mail sent by Saatchi to Lawson in October was read out by the defense . In the e-mail , 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 . '' Giving evidence Friday in the west London court , Saatchi said he was `` bereft '' that the e-mail -- in which he said he `` believed '' what the sisters claimed about Lawson 's drug use -- had been made public . He said he never saw his wife taking drugs during their 10-year marriage and that he had no hard evidence she had done so . But he testified that the accusation `` sounded pretty compelling to me . '' The allegations emerged in June , around the time that 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 . 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 was not able to say whether Lawson had approved them , he said . Earlier , Saatchi described the sisters ' roles as housekeeping , organizing the household and helping out with any tasks needed by the family . They were first employed by Lawson and then by his company , he said . Saatchi said he was aware the two sisters were given credit cards in order to pay for household expenses . This was his ex-wife 's idea , he told the court . Asked about the sisters ' role when Lawson 's children grew older , Saatchi said : `` I 'm very fond of Francesca and Lisa ( Elisabetta ) and they were part of our family ... The children were fond of them , we did n't want them to go , so they stayed with us as housekeepers and for general assistance . '' Designer labels . The first witness in the case , Rahul Gajjar , an accountant for Saatchi , told the court Thursday that Francesca had 64,336.97 pounds ( $ 104,500 ) in expenses on her company credit card in June 2012 . Among the expenses were purchases from designer labels Prada , Miu Miu , Louis Vuitton and Chloe , as well as hotel bills and plane tickets . The court heard that Francesca 's average monthly expenditures were 48,000 pounds and Elisabetta 's were 28,000 pounds , whereas other personal assistants to Saatchi , a well-known art collector , spent a maximum of 8,000 pounds a month . The sisters were expected to make purchases for the household on the company credit card , Gajjar said . But the prosecution says they spent large sums of money on themselves . Drug use claims . Isleworth Crown Court heard at a pretrial hearing for the sisters this week that Lawson and Saatchi had a `` culture of secrecy '' around their marriage . Representatives for Lawson declined to comment on the drug allegations then , citing the ongoing court proceedings . The defense alleged that the e-mails showed both Saatchi and Lawson had attempted a `` manipulation of the court '' and that the case should be thrown out . The judge ruled the trial would proceed . The prosecution told the court Wednesday that the two sisters spent about 685,000 pounds ( $ 1.1 million ) on company credit cards over the course of four years , according to UK media reports . 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 .
Elisabetta Grillo says he never saw Nigella Lawson take drugs but he believes she did . Saatchi says he did not authorize more than $ 1 million in spending by the accused . Ex-aides Saatchi and Charles Saatchi deny embezzling money from Francesca , Nigella Lawson . Representatives for Nigella Lawson have not commented on the drugs claims .