Three former employees of Barclays Bank have been charged by the Serious Fraud Office (SFO) in connection with its investigation into the manipulation of Libor, the inter-bank lending rate.The SFO said in a statement that Peter Charles Johnson, Jonathan James Mathew and Stylianos Contogoulas, had been charged with conspiracy to defraud between June 1st 2005 and August 31st 2007.In 2013 Barclays was fined £290m in the UK and US after some of its traders were caught trying to rig the Libor rate.The investigation started in July 2012 and is still ongoing, the SFO said. It is collaborating with the UK Financial Conduct Authority and the United States Department of Justice on their respective ongoing investigations into the scandal.FP