Francesca and Elisabetta Grillo
Francesca and Elisabetta Grillo arrive at Isleworth Crown Court.

The millionaire art dealer and advertising guru, Charles Saatchi arrived at Isleworth Crown Court today (29 November) to give evidence against his two former personal assistants, who are on trial accused of fraud.

Sisters Francesca, 35, and 41-year-old Elisabetta Grillo, former employees of the businessman, are accused of using company credit cards loaned to them, to buy an array of personal luxury items to the tune of £685,000.

The Italian sisters, who have been working for Saatchi as a housekeeper and nanny for many years, seemed to have developed a taste for the high life, with the 70-year-old unawares that, all the while, he had been footing the bill for their extravagant lifestyle.

Finance director, Rahul Gajjar told the court that Saatchi's wife TV chef Nigella Lawson and five personal assistants including the Grillo sisters, had been issued credit cards which were intended to be used for "personal spending for Nigella and the family".

70 year-old Saatchi confirmed this saying: 'If they were taking the children on holiday they would be paying for everything - the hotel bills, the meals, and they would also be given some money that the children were allowed to spend.'

The sisters' monthly spending was however in excess of their annual salaries, which were £28,000 for Francesca and £25,000 for Elisabetta.

Embarking on a non-stop shopping spree, the Italian siblings lavished themselves with luxury goods, entirely at Saatchi's expense.

They maxed out the credit cards, spending £5,000 on designer clothes in a single transaction in clothes store Miu Miu. £2,650 was spent at Prada in one day and £2,300 at luxury handbag designers Louis Vuitton.

Payments were allegedly made from the company coffers for luxury designer items such as Marc Jacobs, Calvin Klein, Vivienne Westwood and Christian Dior. And in a bid to keep up the image, there were visits to health spas, payments for dental treatment and visits to the hairdresser, all paid for by the millionaire art collector. He just didn't know it.

The sisters were also believed to have been using the company credit card when purchasing transatlantic plane tickets and for stays at luxury hotels in New York and The Ritz in Paris, as they lived the celebrity lifestyle.

While Miss Lawson's spending on the credit cards averaged £7,000 per month. Francesca, 35, averaged £48,000 per month in the four months to June 2012, while her 41-year-old sister averaged £28,000.

Credit card statements showed that in June 2012 Francesca had spent £64,336 on the Coutts bank credit card issued by Saatchi. She is said to have admitted to Mr Gajjar that £33,893 of that was "unauthorised".

Asked whether the credit card bills were checked, Mr Gajjar said: "The credit cards went through Charles's personal account so they weren't analysed."

The Grillo sisters suspect spending habits were only rumbled when Saatchi discovered one of them had ordered a taxi on his account to go to a polo match in Berkshire.

Midst claims they "were being treated worse than Filipino slaves," the sisters denied the charges made by the couple, and claim that they were given free reign in exchange for keeping silent about Nigella Lawson's alleged drug use.

Lawson is expected to appear in court next week to give evidence in the trial.