By Martin HickmanRupert Murdoch's British newspaper group was fearful of attack and surveillance from hostile forces in 2011, the hacking trial was told today.The jury at the Old Bailey heard that in the year the News of the World closed, security chief Mark Hanna swept News International's offices for listening devices, intercepted threatening letters to executives and monitored demonstrations outside its HQ in Wapping, east London.By July 2011, said William Clegg, QC, representing Mr Hanna, NI's group director of security had been working for three weeks without a single day's break.With Mrs Brooks and her husband Charlie, Mr Hanna is on trial accused of conspiring to pervert the course of justice between 15-19 July 2011 by hiding evidence from the police inquiry into phone hacking.Painting a picture of Mr Hanna's broad responsibilities, Mr Clegg said they ranged from ensuring the safety of fire exits to thwarting commercial espionage.Checking for bugs had become routine at News International's HQ in Wapping, the lawyer told the court, given that newspapers were anxious to protect scoops and that the company was bidding to increase its shareholding in BSkyB.He quoted an email sent by Mrs Brooks to general manager Will Lewis (and copied to Mr Hanna) on 25 January 2011 in which NI's chief executive wrote: "Can we have my phones and office swept... thanks. discreetly."Mr Clegg, asking his first questions during the three-month trial, added that Mrs Brooks's car and flat at Chelsea Harbour were also swept.He asked Jane Viner, NI's head of facilities: "A perfectly routine request for an executive at that time?", to which Mrs Viner, Mr Hanna's line manager, replied: "Yes."She agreed that it was Mr Hanna's job to provide extra security to executives when necessary and that he had told her that he was intercepting suspicious letters addressed to executives.Mr Clegg told the court that as part of his duties in 2011, Mr Hanna had employed a firm called International Corporate Protection to guard three executives: Mrs Brooks, Mr Lewis and Simon Greenberg. He added that Mrs Brooks was given the codename Black Hawk, while the other codenames were Kestrel and Sparrowhawk. By mid-July, Mr Clegg said, Mr Hanna was working long days and taking work home in the evening.As demonstrators converged sporadically on Thomas More Square, Wapping, after the disclosure that the News of the World had hacked Milly Dowler's phone, Mr Hanna wrote to Mrs Viner on 14 July: "I am constantly reviewing the security arrangements."Mr Hanna went on: "We are intercepting some executive mail in relation to threatening correspondence. We have also received similar emails."Mr Hanna, whom the court was told was a veteran of the first Gulf War, explained that he had carried out an anti-surveillance "masking" of the perimeter of Thomas More Square.Mrs Viner agreed with Mr Clegg that she had become concerned at his pastoral well-being, referring to it in a report she emailed to her boss, group finance director Susan Panuccio.Mrs Viner, who previously said that Mr Hanna was trustworthy and hardworking, told the jury: "Yes, I was concerned about Mark's welfare."The case, which is expected to last for another three months, continues.