LONDON (Reuters) - Britain's financial regulators are probing historical links between Barclays Chief Executive Jes Staley and the U.S. financier Jeffrey Epstein, who killed himself while awaiting trial on sex trafficking charges, the bank said on Thursday.Barclays said its board had looked into media reports on Staley's relationship with Epstein, and probed Staley's characterisation of it. The Financial Conduct Authority and the Prudential Regulation Authority are investigating. The bank said..