A News UK employee has testified in court that staff "worked in fear" of Rebekah Brooks when she edited the Sun as "people were hired and fired on a regular basis".The testimony came in the fourth week of the trial of four of the paper's journalists who are facing charges relating to alleged payments to public officials for confidential. Charlotte Hull, a former administrative assistant to The Sun's Newsdesk, the jury heard, was responsible for administrating the system of cash payments for sources at the daily tabloid and confirmed that from 2008 every one had to be approved by the editor.Asked if anyone ever offered The Sun a story without asking for payment? Hull replied "I can't think of a single time". She also told the court she had never been told not to pay public officials for contributions and there was no system in place to prevent it happening.The jury also heard evidence from retired Detective Superintendent Mark Kandiah who was the senior officer in Operation Elveden, the Metropolitan police's investigation into alleged corrupt payments by newspapers. The witness told the court that the operation began when the police were given information that a royal correspondent at the now defunct News of the World may have been paying police officers. However, it quickly expanded to take in other allegations of corruption at one point employing more than 30 officers.Under questioning from defence counsel the retired police officer said that due to the specific legal issues around investigating newspapers a "memorandum of understanding" had been negotiated with News International about what information was to be given to the police. Kandiah said that there was no way of knowing" if all the relevant documents had been handed over, a situation that he described as "less than satisfactory". There had also been, he agreed, a large number of emails that had been deleted from the company's computer system. "We don't know if we've got everything" the witness confirmed.As well as the four Sun reporters, John Kay, Duncan Larcombe, Fergus Shanahan and Geoffrey Webster, an army officer John Hardy and his wife, Claire, are also in the dock.All of the defendants deny all of the charges, the trial continues.