I agree with merrymouse and Bonsoir that it does seem lax. I don't know what the rules are.
"During cross-examination by Karina Arden, representing Francesca, Mr Gajjar said it was he who authorised the defendant's credit limit, which started off at £25,000.
Mr Gajjar said he increased it to £50,000 in February 2010 and then £100,000 in June 2011 as the defendant kept going over the limit and her card was frozen.
Ms Arden asked: ''So the level of spending, which may be suggested by the Crown to be extraordinary - certainly you and Charles knew about it?''
''Yes,'' Mr Gajjar replied.
Ms Arden went on: ''He knew that a credit limit of £50,000 was insufficient at one point and therefore asked for it to be increased?''
''The details of the figure I don't think Charles was aware of,'' Mr Gajjar said.
Asked why Francesca and Elisabetta, 41, were expected to buy so much for the household, Mr Gajjar said: ''Charles and Nigella didn't generally go shopping like most people do. They would have their personal assistants shop for them.''
www.telegraph.co.uk/news/uknews/law-and-order/10483355/Charles-Saatchis-accountant-admits-increasing-limit-on-aides-credit-card-to-100000.html
Apparently, Saatchi does not know how the card bills were settled
"The multimillionaire art dealer Charles Saatchi was unsure how credit card bills run up by his personal assistants and totalling tens of thousands of pounds a month were settled, a court has heard.
....
They had been given company credit cards in the name of Saatchi's company, Conarco, for their work as housekeepers and assistants, he said, along with three other personal assistants.
Asked by Jane Carpenter, prosecuting, if he could tell her how the expenditure on the cards was discharged, he said: "I can't … I'm sorry, I don't know." Pressed on the point, he added: "I am pretty certain that the company pays off everything and then bills me and I pay the company back for anything that's personal."
www.theguardian.com/uk-news/2013/nov/29/charles-saatchi-nigella-lawson-assistants-credit-cards